original_problem stringlengths 15 7.47k | original_reasoning_trace stringlengths 71 77.5k | conversations listlengths 2 2 |
|---|---|---|
Three vertices of parallelogram $PQRS$ are $P(-3,-2), Q(1,-5), R(9,1)$ with $P$ and $R$ diagonally opposite.
The sum of the coordinates of vertex $S$ is:
$\textbf{(A)}\ 13 \qquad \textbf{(B)}\ 12 \qquad \textbf{(C)}\ 11 \qquad \textbf{(D)}\ 10 \qquad \textbf{(E)}\ 9$ | <think>
Okay, so I need to find the coordinates of vertex S in the parallelogram PQRS, where three vertices are given: P(-3,-2), Q(1,-5), and R(9,1). P and R are diagonally opposite, which means S and Q must also be diagonally opposite. The question asks for the sum of the coordinates of S once we find them. The answer... | [
{
"from": "human",
"value": "Three vertices of parallelogram $PQRS$ are $P(-3,-2), Q(1,-5), R(9,1)$ with $P$ and $R$ diagonally opposite. \nThe sum of the coordinates of vertex $S$ is:\n$\\textbf{(A)}\\ 13 \\qquad \\textbf{(B)}\\ 12 \\qquad \\textbf{(C)}\\ 11 \\qquad \\textbf{(D)}\\ 10 \\qquad \\textbf{(E)}... |
In an equilateral triangle $A B C$ with a side length of $8 \mathrm{~cm}$, point $D$ is the midpoint of side $B C$ and point $E$ is the midpoint of side $A C$. Point $F$ lies on segment $B C$ such that the area of triangle $A B F$ is equal to the area of quadrilateral $A B D E$.
Calculate the length of segment $B F$.
... | <think>
Okay, let's tackle this geometry problem. So, we have an equilateral triangle ABC with each side being 8 cm. Point D is the midpoint of BC, and point E is the midpoint of AC. We need to find the length of segment BF, where point F is on BC such that the area of triangle ABF is equal to the area of quadrilateral... | [
{
"from": "human",
"value": "In an equilateral triangle $A B C$ with a side length of $8 \\mathrm{~cm}$, point $D$ is the midpoint of side $B C$ and point $E$ is the midpoint of side $A C$. Point $F$ lies on segment $B C$ such that the area of triangle $A B F$ is equal to the area of quadrilateral $A B D E$... |
Three generous friends, each with some money, redistribute the money as followed:
Amy gives enough money to Jan and Toy to double each amount has.
Jan then gives enough to Amy and Toy to double their amounts.
Finally, Toy gives enough to Amy and Jan to double their amounts.
If Toy had 36 dollars at the beginning and 3... | <think>
Okay, let's see. There are three friends: Amy, Jan, and Toy. Toy started with $36 and ended with $36. The problem is asking for the total amount of money all three have together. The answer choices are numbers like 108, 180, 216, etc. So, the total is one of those, and we need to figure it out based on the tran... | [
{
"from": "human",
"value": "Three generous friends, each with some money, redistribute the money as followed:\nAmy gives enough money to Jan and Toy to double each amount has.\nJan then gives enough to Amy and Toy to double their amounts. \nFinally, Toy gives enough to Amy and Jan to double their amounts.\... |
Solve the following system of equations:
$$
\sqrt[3]{a^{y}}=\sqrt{\frac{a^{13}}{a^{x}}}
$$
$$
\sqrt[7]{a^{3 x}} \cdot \sqrt[9]{a^{4 y}}=a^{7}
$$ | <think>
Okay, let me try to solve this system of equations. Hmm, the equations involve exponents and radicals, so maybe I can simplify them using properties of exponents. Let me start with the first equation: the cube root of a to the power y equals the square root of (a^13 divided by a^x). Let me write that down more ... | [
{
"from": "human",
"value": "Solve the following system of equations:\n\n$$\n\\sqrt[3]{a^{y}}=\\sqrt{\\frac{a^{13}}{a^{x}}}\n$$\n\n$$\n\\sqrt[7]{a^{3 x}} \\cdot \\sqrt[9]{a^{4 y}}=a^{7}\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let me try to solve this system of equations. Hmm, the equat... |
5. In the sequence $\left\{a_{n}\right\}$, $a_{1}=2, a_{n}+a_{n+1}=1\left(n \in \mathbf{N}_{+}\right)$, let $S_{n}$ be the sum of the first $n$ terms of the sequence $a_{n}$, then the value of $S_{2017}-$ $2 S_{2018}+S_{2019}$ is $\qquad$ | <think>
Okay, let's see. I need to solve this problem involving a sequence and some sums. Let me start by understanding what's given and what's being asked.
First, the sequence {a_n} has the first term a₁ = 2. Then there's a recursive relation: aₙ + a_{n+1} = 1 for any positive integer n. So, each term plus the next t... | [
{
"from": "human",
"value": "5. In the sequence $\\left\\{a_{n}\\right\\}$, $a_{1}=2, a_{n}+a_{n+1}=1\\left(n \\in \\mathbf{N}_{+}\\right)$, let $S_{n}$ be the sum of the first $n$ terms of the sequence $a_{n}$, then the value of $S_{2017}-$ $2 S_{2018}+S_{2019}$ is $\\qquad$"
},
{
"from": "gpt",
... |
From a barrel, we pour out 4 liters of wine and replace it with 4 liters of water. From the resulting mixture, we again pour out 4 liters and replace it with 4 liters of water. We repeat this process a total of three times, and in the final result, there is 2.5 liters more water than wine. How many liters of wine were ... | <think>
Okay, so I have this problem where we start with a barrel of wine. Then, we pour out 4 liters of wine and replace it with 4 liters of water. We do this three times total, and after the third time, there's 2.5 liters more water than wine. The question is, how many liters of wine were originally in the barrel?
H... | [
{
"from": "human",
"value": "From a barrel, we pour out 4 liters of wine and replace it with 4 liters of water. From the resulting mixture, we again pour out 4 liters and replace it with 4 liters of water. We repeat this process a total of three times, and in the final result, there is 2.5 liters more water... |
XLVII OM - I - Problem 2
A palindromic number is defined as a natural number whose decimal representation read from left to right is the same as when read from right to left. Let $ (x_n) $ be the increasing sequence of all palindromic numbers. Determine all prime numbers that are divisors of at least one of the differ... | <think>
Okay, so I have this problem about palindromic numbers and their differences. The question is asking for all prime numbers that can divide at least one of the differences between consecutive palindromic numbers. Hmm, let's start by recalling what a palindromic number is. It's a number that reads the same forwar... | [
{
"from": "human",
"value": "XLVII OM - I - Problem 2\n\nA palindromic number is defined as a natural number whose decimal representation read from left to right is the same as when read from right to left. Let $ (x_n) $ be the increasing sequence of all palindromic numbers. Determine all prime numbers that... |
4. The area of a rectangle is 180 units $^{2}$ and the perimeter is 54 units. If the length of each side of the rectangle is increased by six units, what is the area of the resulting rectangle? | <think>
Okay, so I have this problem here about a rectangle. The area is 180 units squared and the perimeter is 54 units. Then, each side is increased by six units, and I need to find the new area. Hmm, let me think about how to approach this.
First, I remember that for a rectangle, the area is length times width, and... | [
{
"from": "human",
"value": "4. The area of a rectangle is 180 units $^{2}$ and the perimeter is 54 units. If the length of each side of the rectangle is increased by six units, what is the area of the resulting rectangle?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I have this problem here... |
160. Solve the equation in integers
$$
x^{2}+x=y^{4}+y^{3}+y^{2}+y
$$ | <think>
Okay, so I need to solve the equation \( x^{2} + x = y^{4} + y^{3} + y^{2} + y \) for integers x and y. Hmm, let's see. Since both sides are polynomials, maybe I can factor them or find some bounds to limit possible values of y and x.
First, let me try to understand the right-hand side. The right side is \( y^... | [
{
"from": "human",
"value": "160. Solve the equation in integers\n\n$$\nx^{2}+x=y^{4}+y^{3}+y^{2}+y\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to solve the equation \\( x^{2} + x = y^{4} + y^{3} + y^{2} + y \\) for integers x and y. Hmm, let's see. Since both sides are polynomia... |
6. For natural numbers $a, b, c$, define the operation * such that it satisfies
$$
\begin{array}{l}
(a * b) * c=a *(b c), \\
(a * b)(a * c)=a *(b+c) .
\end{array}
$$
Then the value of $3 * 4$ is ( ).
(A) 12
(B) 64
(C) 81
(D) None of the above | <think>
Okay, let me try to figure out this problem. So, we have an operation * defined for natural numbers a, b, c. There are two properties given:
1. (a * b) * c = a * (b c)
2. (a * b)(a * c) = a * (b + c)
And we need to find the value of 3 * 4, with the options being 12, 64, 81, or none of the above.
First, let ... | [
{
"from": "human",
"value": "6. For natural numbers $a, b, c$, define the operation * such that it satisfies\n$$\n\\begin{array}{l}\n(a * b) * c=a *(b c), \\\\\n(a * b)(a * c)=a *(b+c) .\n\\end{array}\n$$\n\nThen the value of $3 * 4$ is ( ).\n(A) 12\n(B) 64\n(C) 81\n(D) None of the above"
},
{
"from... |
7. In a free-throw test, a person only needs to make 3 shots to pass and does not need to continue shooting, but each person can shoot at most 5 times. The probability that a player with a shooting accuracy of $\frac{2}{3}$ passes the test is . $\qquad$ | <think>
Okay, so here's this problem about a free-throw test. Let me read it again: A person needs to make 3 shots to pass and doesn't need to continue shooting after that, but each person can shoot at most 5 times. The player has a shooting accuracy of 2/3. We need to find the probability that the player passes the te... | [
{
"from": "human",
"value": "7. In a free-throw test, a person only needs to make 3 shots to pass and does not need to continue shooting, but each person can shoot at most 5 times. The probability that a player with a shooting accuracy of $\\frac{2}{3}$ passes the test is . $\\qquad$"
},
{
"from": "... |
$4 \cdot 103$ real numbers $\alpha, \beta$ satisfy the system of equations
$$
\left\{\begin{array}{l}
\alpha^{3}-3 \alpha^{2}+5 \alpha-17=0 \\
\beta^{3}-3 \beta^{2}+5 \beta+11=0 .
\end{array}\right.
$$
Find $\alpha+\beta$. | <think>
Okay, let me see. So I have this problem where there are two real numbers, α and β, that satisfy these two cubic equations:
First equation: α³ - 3α² + 5α - 17 = 0
Second equation: β³ - 3β² + 5β + 11 = 0
And I need to find α + β. Hmm, interesting. Both equations are cubic and look very similar except for the ... | [
{
"from": "human",
"value": "$4 \\cdot 103$ real numbers $\\alpha, \\beta$ satisfy the system of equations\n$$\n\\left\\{\\begin{array}{l}\n\\alpha^{3}-3 \\alpha^{2}+5 \\alpha-17=0 \\\\\n\\beta^{3}-3 \\beta^{2}+5 \\beta+11=0 .\n\\end{array}\\right.\n$$\n\nFind $\\alpha+\\beta$."
},
{
"from": "gpt",
... |
20. Ruth and Sarah decide to have a race. Ruth runs around the perimeter of the pool shown in the diagram while Sarah swims lengths of the pool.
Ruth runs three times as fast as Sarah swims. Sarah swims six lengths of the pool in the same time Ruth runs around the pool five times.
How wide is the pool?
A $25 \mathrm{~m... | <think>
Okay, let's try to figure out the width of the pool. Hmm, the problem says Ruth runs around the perimeter of the pool while Sarah swims lengths of it. Ruth runs three times as fast as Sarah swims. Also, Sarah swims six lengths in the same time Ruth runs around the pool five times. The question is asking for the... | [
{
"from": "human",
"value": "20. Ruth and Sarah decide to have a race. Ruth runs around the perimeter of the pool shown in the diagram while Sarah swims lengths of the pool.\nRuth runs three times as fast as Sarah swims. Sarah swims six lengths of the pool in the same time Ruth runs around the pool five tim... |
## Task 1 - 220831
On a day in 1981, Cathrin asks her grandfather about his birth year. The grandfather, a friend of puzzle questions, replied:
"I am older than 65 years, but younger than 100 years. The year of my birth is not divisible by 2, 3, or 5. The remainder when this year is divided by 60 is not a prime numbe... | <think>
Okay, let's try to figure out the grandfather's birth year based on the clues given. So, Cathrin asked her grandfather in 1981, and he gave some hints about his birth year. Let me break down each clue step by step.
First, the grandfather says he's older than 65 but younger than 100. Since this conversation is ... | [
{
"from": "human",
"value": "## Task 1 - 220831\n\nOn a day in 1981, Cathrin asks her grandfather about his birth year. The grandfather, a friend of puzzle questions, replied:\n\n\"I am older than 65 years, but younger than 100 years. The year of my birth is not divisible by 2, 3, or 5. The remainder when t... |
## Task A-1.5.
How many four-digit numbers divisible by 3 do not contain the digits $2, 4, 6$ or 9 in their decimal representation? | <think>
Okay, so I need to figure out how many four-digit numbers are divisible by 3 and don't contain the digits 2, 4, 6, or 9. Let me start by breaking down the problem step by step.
First, a four-digit number ranges from 1000 to 9999. The first digit can't be zero, right? So the thousands place has to be from 1 to ... | [
{
"from": "human",
"value": "## Task A-1.5.\n\nHow many four-digit numbers divisible by 3 do not contain the digits $2, 4, 6$ or 9 in their decimal representation?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to figure out how many four-digit numbers are divisible by 3 and don't conta... |
7. The volume of a cube in cubic metres and its surface area in square metres is numerically equal to four-thirds of the sum of the lengths of its edges in metres.
What is the total volume in cubic metres of twenty-seven such cubes? | <think>
Okay, let's try to figure out this cube problem. So, the problem says that the volume of a cube in cubic meters is numerically equal to four-thirds of the sum of the lengths of its edges. Also, the surface area in square meters is equal to the same four-thirds of the sum of the edges. Wait, actually, let me che... | [
{
"from": "human",
"value": "7. The volume of a cube in cubic metres and its surface area in square metres is numerically equal to four-thirds of the sum of the lengths of its edges in metres.\nWhat is the total volume in cubic metres of twenty-seven such cubes?"
},
{
"from": "gpt",
"value": "<t... |
Find all functions \( f: \mathbb{R} \rightarrow \mathbb{R} \) such that for all real numbers \( x, y \), we have:
\[
f\left(x^{2}-y^{2}\right)=x f(x)-y f(y)
\]
(USAMO 2002) | <think>
Okay, so I need to find all functions \( f: \mathbb{R} \rightarrow \mathbb{R} \) that satisfy the equation \( f(x^{2} - y^{2}) = x f(x) - y f(y) \) for all real numbers \( x \) and \( y \). Hmm, this is a functional equation problem. Let me start by recalling some strategies for solving such problems. Usually, ... | [
{
"from": "human",
"value": "Find all functions \\( f: \\mathbb{R} \\rightarrow \\mathbb{R} \\) such that for all real numbers \\( x, y \\), we have:\n\n\\[\nf\\left(x^{2}-y^{2}\\right)=x f(x)-y f(y)\n\\]\n\n(USAMO 2002)"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find all functio... |
1. Using this picture we can observe that
$$
1+3+5+7=4 \times 4 \text {. }
$$
What is the value of
$$
1+3+5+7+9+11+13+15+17+19+21 ?
$$ | <think>
Okay, let's see. The problem here is about finding the sum of a series of odd numbers: 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21. The example given is 1 + 3 + 5 + 7, which equals 4 times 4, so 16. That makes sense because 1+3 is 4, then +5 is 9, then +7 is 16. Wait, that's actually the squares of the numb... | [
{
"from": "human",
"value": "1. Using this picture we can observe that\n$$\n1+3+5+7=4 \\times 4 \\text {. }\n$$\n\nWhat is the value of\n$$\n1+3+5+7+9+11+13+15+17+19+21 ?\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. The problem here is about finding the sum of a series of odd num... |
A [i]normal magic square[/i] of order $n$ is an arrangement of the integers from $1$ to $n^2$ in a square such that the $n$ numbers in each row, each column, and each of the two diagonals sum to a constant, called the [i]magic sum[/i] of the magic square. Compute the magic sum of a normal magic square of order $8$. | <think>
Okay, so I need to find the magic sum of a normal magic square of order 8. Hmm, let me think. A magic square is a square grid where the numbers in each row, column, and both main diagonals add up to the same number, called the magic sum. Since it's a normal magic square, it uses the numbers from 1 to n², where ... | [
{
"from": "human",
"value": "A [i]normal magic square[/i] of order $n$ is an arrangement of the integers from $1$ to $n^2$ in a square such that the $n$ numbers in each row, each column, and each of the two diagonals sum to a constant, called the [i]magic sum[/i] of the magic square. Compute the magic sum o... |
Task B-4.3. (20 points) What are the minimum and maximum of the function
$$
y=\frac{\sin ^{2} x-\sin x+1}{\sin ^{2} x+\sin x+1}
$$
For which $x \in[0,2 \pi]$ does the function take its minimum, and for which its maximum value? | <think>
Okay, so I need to find the minimum and maximum values of the function y = (sin²x - sinx + 1)/(sin²x + sinx + 1) for x in [0, 2π]. Hmm, let's see. First, since both the numerator and denominator are expressions involving sinx, maybe I can simplify this by letting t = sinx. That way, the function becomes y = (t²... | [
{
"from": "human",
"value": "Task B-4.3. (20 points) What are the minimum and maximum of the function\n\n$$\ny=\\frac{\\sin ^{2} x-\\sin x+1}{\\sin ^{2} x+\\sin x+1}\n$$\n\nFor which $x \\in[0,2 \\pi]$ does the function take its minimum, and for which its maximum value?"
},
{
"from": "gpt",
"val... |
(9 Given the function $f(x)=\cos ^{2} \theta x+\cos \theta x \sin \theta x$ has the smallest positive period of $\frac{\pi}{2}$, then the maximum value of $\theta f(x)$ is $\qquad$ . | <think>
Okay, let's see. I need to find the maximum value of θ times f(x), given that the smallest positive period of the function f(x) = cos²(θx) + cos(θx)sin(θx) is π/2. Hmm, first, maybe I should start by understanding the period of the given function.
The function f(x) is a combination of cos squared and a product... | [
{
"from": "human",
"value": "(9 Given the function $f(x)=\\cos ^{2} \\theta x+\\cos \\theta x \\sin \\theta x$ has the smallest positive period of $\\frac{\\pi}{2}$, then the maximum value of $\\theta f(x)$ is $\\qquad$ ."
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. I need to find th... |
$\frac{1}{4}$ of 100 is equal to
(A) $20 \%$ of 200
(B) $10 \%$ of 250
(C) $15 \%$ of 100
(D) $25 \%$ of 50
(E) $5 \%$ of 300 | <think>
Okay, let's see. The problem is asking me to figure out which of the options (A) through (E) is equal to 1/4 of 100. Alright, let's start by calculating what 1/4 of 100 is.
So, 1/4 of 100... Well, 100 divided by 4 is 25. Right? Because 4 times 25 is 100. So, 1/4 of 100 is 25. Got that down. Now, I need to che... | [
{
"from": "human",
"value": "$\\frac{1}{4}$ of 100 is equal to\n(A) $20 \\%$ of 200\n(B) $10 \\%$ of 250\n(C) $15 \\%$ of 100\n(D) $25 \\%$ of 50\n(E) $5 \\%$ of 300"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. The problem is asking me to figure out which of the options (A) through (... |
## 162. Math Puzzle $11 / 78$
Assume that a fly lays 120 eggs at the beginning of summer, on June 21st, and after 20 days, fully developed insects emerge from these eggs, each of which then lays 120 eggs. How many "descendants" would this fly have in total by the beginning of autumn? | <think>
Okay, so I need to figure out how many descendants the original fly has by the beginning of autumn, which is September 21st, right? Let me break this down step by step.
First, the timeline. The fly lays 120 eggs on June 21st. Then, after 20 days, those eggs hatch into adult flies, each of which also lays 120 ... | [
{
"from": "human",
"value": "## 162. Math Puzzle $11 / 78$\n\nAssume that a fly lays 120 eggs at the beginning of summer, on June 21st, and after 20 days, fully developed insects emerge from these eggs, each of which then lays 120 eggs. How many \"descendants\" would this fly have in total by the beginning ... |
3. Let $a_{1}, a_{2}, \cdots, a_{n}$ represent any permutation of the integers $1,2, \cdots, n$. Let $f(n)$ be the number of such permutations such that
(i) $a_{1}=1$;
(ii) $\left|a_{i}-a_{i+1}\right| \leqslant 2 . i=1,2, \cdots, n-1$.
Determine whether $f(1996)$ is divisible by 3. | <think>
Okay, let's try to figure out whether f(1996) is divisible by 3. So first, let's understand what the problem is asking for. We need to find the number of permutations of the integers from 1 to n (where n is 1996 in this case) that satisfy two conditions: (i) the first element is 1, and (ii) the absolute differe... | [
{
"from": "human",
"value": "3. Let $a_{1}, a_{2}, \\cdots, a_{n}$ represent any permutation of the integers $1,2, \\cdots, n$. Let $f(n)$ be the number of such permutations such that\n(i) $a_{1}=1$;\n(ii) $\\left|a_{i}-a_{i+1}\\right| \\leqslant 2 . i=1,2, \\cdots, n-1$.\nDetermine whether $f(1996)$ is div... |
Given an integer $\mathrm{n} \geq 3$, let $\mathrm{A}_{1}, \mathrm{~A}_{2}, \ldots, \mathrm{~A}_{2 \mathrm{n}}$ be pairwise distinct non-empty subsets of the set $\{1,2, \ldots, \mathrm{n}\}$, and let $A_{2 n+1}=A_{1}$. Find the maximum value of $\sum_{i=1}^{2 n} \frac{\left|A_{i} \cap A_{i+1}\right|}{\left|A_{i}\right... | <think>
Okay, so I need to find the maximum value of this sum: the sum from i=1 to 2n of (|A_i ∩ A_{i+1}|)/(|A_i| * |A_{i+1}|), where each A_i is a distinct non-empty subset of {1,2,...,n}, and A_{2n+1} is set to A_1. Hmm. Alright, let me break this down.
First, the problem is about arranging 2n distinct non-empty sub... | [
{
"from": "human",
"value": "Given an integer $\\mathrm{n} \\geq 3$, let $\\mathrm{A}_{1}, \\mathrm{~A}_{2}, \\ldots, \\mathrm{~A}_{2 \\mathrm{n}}$ be pairwise distinct non-empty subsets of the set $\\{1,2, \\ldots, \\mathrm{n}\\}$, and let $A_{2 n+1}=A_{1}$. Find the maximum value of $\\sum_{i=1}^{2 n} \\f... |
3. In the regular triangular frustum $A^{\prime} B^{\prime} C^{\prime}-A B C$, $A^{\prime} B^{\prime} : A B = 5 : 7$, the sections $A B C^{\prime}$ and $A^{\prime} B C^{\prime}$ divide the frustum into three pyramids $C^{\prime}-A B C$, $B-A^{\prime} B^{\prime} C^{\prime}$, and $C^{\prime}-A A B A^{\prime}$. The volume... | <think>
Alright, let's tackle this problem step by step. First, I need to visualize the regular triangular frustum. A frustum is like a pyramid with the top cut off by a plane parallel to the base. Since it's a regular triangular frustum, both the base ABC and the top face A'B'C' are equilateral triangles. The ratio of... | [
{
"from": "human",
"value": "3. In the regular triangular frustum $A^{\\prime} B^{\\prime} C^{\\prime}-A B C$, $A^{\\prime} B^{\\prime} : A B = 5 : 7$, the sections $A B C^{\\prime}$ and $A^{\\prime} B C^{\\prime}$ divide the frustum into three pyramids $C^{\\prime}-A B C$, $B-A^{\\prime} B^{\\prime} C^{\\p... |
3.20. Calculate
$$
\int_{1}^{i} \frac{\ln ^{2} z}{z} d z
$$ | <think>
Okay, let's see. I need to compute the integral from 1 to i of (ln z)^2 / z dz. Hmm. Alright, complex integrals. So first, I remember that when integrating complex functions, the path of integration matters unless the function is analytic in a simply connected domain containing the path. Wait, is 1/z analytic? ... | [
{
"from": "human",
"value": "3.20. Calculate\n\n$$\n\\int_{1}^{i} \\frac{\\ln ^{2} z}{z} d z\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. I need to compute the integral from 1 to i of (ln z)^2 / z dz. Hmm. Alright, complex integrals. So first, I remember that when integrating com... |
Example 6 Solve the system of equations $\left\{\begin{array}{l}x+y+z=3, \\ x^{2}+y^{2}+z^{2}=3,(\text{Example 4 in [1]}) \\ x^{5}+y^{5}+z^{5}=3 .\end{array}\right.$ | <think>
Okay, let's try to solve this system of equations. So, we have three equations:
1. \( x + y + z = 3 \)
2. \( x^2 + y^2 + z^2 = 3 \)
3. \( x^5 + y^5 + z^5 = 3 \)
Hmm, this looks interesting. The first equation is linear, the second is quadratic, and the fifth is a fifth-degree equation. I remember from algebra... | [
{
"from": "human",
"value": "Example 6 Solve the system of equations $\\left\\{\\begin{array}{l}x+y+z=3, \\\\ x^{2}+y^{2}+z^{2}=3,(\\text{Example 4 in [1]}) \\\\ x^{5}+y^{5}+z^{5}=3 .\\end{array}\\right.$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's try to solve this system of equations. ... |
6. Given $a, b, c \in [0,1]$. Then
$$
\frac{a}{bc+1}+\frac{b}{ca+1}+\frac{c}{ab+1}
$$
the range of values is | <think>
Okay, so I have this problem here where I need to find the range of the expression \(\frac{a}{bc+1} + \frac{b}{ca+1} + \frac{c}{ab+1}\) given that \(a\), \(b\), and \(c\) are all in the interval \([0,1]\). Hmm, let's see. I need to figure out the minimum and maximum values this expression can take.
First off,... | [
{
"from": "human",
"value": "6. Given $a, b, c \\in [0,1]$. Then\n$$\n\\frac{a}{bc+1}+\\frac{b}{ca+1}+\\frac{c}{ab+1}\n$$\n\nthe range of values is"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I have this problem here where I need to find the range of the expression \\(\\frac{a}{bc+1} + \\fr... |
17. What is the value of the sum: $1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\ldots+\frac{1}{1024}$ ? | <think>
Alright, so I need to find the value of the sum: 1 + 1/2 + 1/4 + 1/8 + ... + 1/1024. Hmm, let's see. I remember that this looks like a geometric series. Let me recall what a geometric series is. It's a series where each term after the first is found by multiplying the previous term by a constant called the comm... | [
{
"from": "human",
"value": "17. What is the value of the sum: $1+\\frac{1}{2}+\\frac{1}{4}+\\frac{1}{8}+\\ldots+\\frac{1}{1024}$ ?"
},
{
"from": "gpt",
"value": "<think>\nAlright, so I need to find the value of the sum: 1 + 1/2 + 1/4 + 1/8 + ... + 1/1024. Hmm, let's see. I remember that this lo... |
9. As shown in the figure, in the right triangle $A B C$, $\angle A C B=\frac{\pi}{2}, A C=B C=2$, point $P$ is a point on the hypotenuse $A B$, and $B P=2 P A$, then $\overrightarrow{C P} \cdot \overrightarrow{C A}+\overrightarrow{C P} \cdot \overrightarrow{C B}=$ $\qquad$ . | <think>
Okay, let me try to figure out this problem. So, we have a right triangle ABC where angle ACB is π/2, which means it's a right angle at point C. The sides AC and BC are both 2 units long. So, triangle ABC is an isosceles right triangle with legs of length 2. The hypotenuse AB must then be 2√2 because in a right... | [
{
"from": "human",
"value": "9. As shown in the figure, in the right triangle $A B C$, $\\angle A C B=\\frac{\\pi}{2}, A C=B C=2$, point $P$ is a point on the hypotenuse $A B$, and $B P=2 P A$, then $\\overrightarrow{C P} \\cdot \\overrightarrow{C A}+\\overrightarrow{C P} \\cdot \\overrightarrow{C B}=$ $\\q... |
## Task 4 - 240624
Rita is experimenting with a balance scale.
(With such a scale, it can be determined whether the content of one pan weighs as much as the content of the other pan or which of the two contents weighs more than the other.)
Rita has 17 balls, 6 cubes, and 1 pyramid. She observes:
(1) Each ball weigh... | <think>
Okay, let's see. Rita has a balance scale and some objects: 17 balls, 6 cubes, and 1 pyramid. The problem states that all balls weigh the same, all cubes weigh the same, and we have two equations relating the weights of these objects. Rolf wants to know how many balls weigh the same as the pyramid. The question... | [
{
"from": "human",
"value": "## Task 4 - 240624\n\nRita is experimenting with a balance scale.\n\n(With such a scale, it can be determined whether the content of one pan weighs as much as the content of the other pan or which of the two contents weighs more than the other.)\n\nRita has 17 balls, 6 cubes, an... |
2. (a) In Figure 1, trapezoid $A B E D$ is formed by joining $\triangle B C E$ (which is rightangled at $C$ ) to rectangle $A B C D$. If $A B=3, C E=6$ and the area of trapezoid $A B E D$ is 48 , determine the length of $B E$.
(b) In Figure 2, circles with centres $P$ and $Q$ touch a line $\ell$ (that is, are tangent t... | <think>
Okay, so I need to solve part (a) of this problem. Let me read it again to make sure I understand.
We have a trapezoid ABED formed by joining triangle BCE, which is right-angled at C, to rectangle ABCD. Given that AB is 3 units, CE is 6 units, and the area of trapezoid ABED is 48. We need to find the length of... | [
{
"from": "human",
"value": "2. (a) In Figure 1, trapezoid $A B E D$ is formed by joining $\\triangle B C E$ (which is rightangled at $C$ ) to rectangle $A B C D$. If $A B=3, C E=6$ and the area of trapezoid $A B E D$ is 48 , determine the length of $B E$.\n(b) In Figure 2, circles with centres $P$ and $Q$ ... |
Natural numbers $k, l,p$ and $q$ are such that if $a$ and $b$ are roots of $x^2 - kx + l = 0$ then $a +\frac1b$ and $b + \frac1a$ are the roots of $x^2 -px + q = 0$. What is the sum of all possible values of $q$? | <think>
Okay, let me try to work through this problem step by step. So, we have two quadratic equations. The first one is \( x^2 - kx + l = 0 \) with roots \( a \) and \( b \). Then, the second quadratic equation is \( x^2 - px + q = 0 \) with roots \( a + \frac{1}{b} \) and \( b + \frac{1}{a} \). We need to find the s... | [
{
"from": "human",
"value": "Natural numbers $k, l,p$ and $q$ are such that if $a$ and $b$ are roots of $x^2 - kx + l = 0$ then $a +\\frac1b$ and $b + \\frac1a$ are the roots of $x^2 -px + q = 0$. What is the sum of all possible values of $q$?"
},
{
"from": "gpt",
"value": "<think>\nOkay, let me... |
1. [4] A hundred friends, including Petya and Vasya, live in several cities. Petya learned the distance from his city to the city of each of the remaining 99 friends and added these 99 numbers. Vasya did the same. Petya got 1000 km. What is the largest number Vasya could have obtained? (Consider the cities as points on... | <think>
Okay, let's see. So there are 100 friends, including Petya and Vasya, living in several cities. The cities are points on a plane, and if two people are in the same city, the distance between them is zero. Petya calculated the sum of distances from his city to each of the other 99 friends, and got 1000 km. Now w... | [
{
"from": "human",
"value": "1. [4] A hundred friends, including Petya and Vasya, live in several cities. Petya learned the distance from his city to the city of each of the remaining 99 friends and added these 99 numbers. Vasya did the same. Petya got 1000 km. What is the largest number Vasya could have ob... |
10.243. Inside an angle of $60^{\circ}$, there is a point located at distances of $\sqrt{7}$ and $2 \sqrt{7}$ cm from the sides of the angle. Find the distance from this point to the vertex of the angle. | <think>
Okay, so there's this geometry problem here. Let me read it again: Inside an angle of 60 degrees, there's a point. This point is sqrt(7) cm away from one side of the angle and 2*sqrt(7) cm away from the other side. We need to find the distance from this point to the vertex of the angle. Hmm, okay. Let me visual... | [
{
"from": "human",
"value": "10.243. Inside an angle of $60^{\\circ}$, there is a point located at distances of $\\sqrt{7}$ and $2 \\sqrt{7}$ cm from the sides of the angle. Find the distance from this point to the vertex of the angle."
},
{
"from": "gpt",
"value": "<think>\nOkay, so there's thi... |
3. [7 points] Let $M$ be a figure on the Cartesian plane consisting of all points $(x, y)$ such that there exists a pair of real numbers $a, b$ for which the system of inequalities is satisfied
$$
\left\{\begin{array}{l}
(x-a)^{2}+(y-b)^{2} \leqslant 20 \\
a^{2}+b^{2} \leqslant \min (8 a-4 b ; 20)
\end{array}\right.
$... | <think>
Okay, so I need to find the area of figure M, which consists of all points (x, y) such that there exist real numbers a and b satisfying two conditions:
1. The point (x, y) lies inside or on the circle centered at (a, b) with radius sqrt(20).
2. The point (a, b) itself lies inside or on the circle defined by a... | [
{
"from": "human",
"value": "3. [7 points] Let $M$ be a figure on the Cartesian plane consisting of all points $(x, y)$ such that there exists a pair of real numbers $a, b$ for which the system of inequalities is satisfied\n\n$$\n\\left\\{\\begin{array}{l}\n(x-a)^{2}+(y-b)^{2} \\leqslant 20 \\\\\na^{2}+b^{2... |
An airplane traces out a regular $n$-sided polygon, and does so at speeds of $v_{1}, v_{2}, \ldots v_{n}$ along each side. What is the average speed of the airplane? | <think>
Okay, let's see. The problem is about an airplane tracing out a regular n-sided polygon, and it has different speeds on each side: v1, v2, ..., vn. We need to find the average speed of the airplane. Hmm, average speed usually involves total distance divided by total time, right? So maybe that's the approach her... | [
{
"from": "human",
"value": "An airplane traces out a regular $n$-sided polygon, and does so at speeds of $v_{1}, v_{2}, \\ldots v_{n}$ along each side. What is the average speed of the airplane?"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. The problem is about an airplane tracing ou... |
6. What is the last digit of $1^{1}+2^{2}+3^{3}+\cdots+100^{100}$ ? | <think>
Okay, so I need to find the last digit of the sum \(1^{1} + 2^{2} + 3^{3} + \cdots + 100^{100}\). Hmm, that seems like a pretty big sum, but since we're only interested in the last digit, maybe there's a pattern or a cycle in the last digits of these exponents that we can exploit. Let me think through this step... | [
{
"from": "human",
"value": "6. What is the last digit of $1^{1}+2^{2}+3^{3}+\\cdots+100^{100}$ ?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find the last digit of the sum \\(1^{1} + 2^{2} + 3^{3} + \\cdots + 100^{100}\\). Hmm, that seems like a pretty big sum, but since we're on... |
1 Convex quadrilateral $E F G H$ has vertices $E, F, G, H$ on the sides $A B, B C, C D, D A$ of convex quadrilateral $A B C D$, respectively, satisfying
$$
\frac{A E}{E B} \cdot \frac{B F}{F C} \cdot \frac{C G}{G D} \cdot \frac{D H}{H A}=1
$$
and points $A, B, C, D$ are on the sides $H_{1} E_{1}, E_{1} F_{1}, F_{1} G_... | <think>
Okay, so I have this problem about convex quadrilaterals and some ratios. Let me try to parse through it step by step.
First, the problem states: There's a convex quadrilateral EFGH with vertices E, F, G, H on the sides AB, BC, CD, DA of another convex quadrilateral ABCD, respectively. These points satisfy the... | [
{
"from": "human",
"value": "1 Convex quadrilateral $E F G H$ has vertices $E, F, G, H$ on the sides $A B, B C, C D, D A$ of convex quadrilateral $A B C D$, respectively, satisfying\n$$\n\\frac{A E}{E B} \\cdot \\frac{B F}{F C} \\cdot \\frac{C G}{G D} \\cdot \\frac{D H}{H A}=1\n$$\n\nand points $A, B, C, D$... |
Let $S\,$ be a set with six elements. In how many different ways can one select two not necessarily distinct subsets of $S\,$ so that the union of the two subsets is $S\,$? The order of selection does not matter; for example, the pair of subsets $\{a, c\},\{b, c, d, e, f\}$ represents the same selection as the pair $\... | <think>
Alright, let's tackle this problem. So, we have a set S with six elements, and we need to find the number of different ways to select two subsets (which can be the same or different) such that their union is S. Also, the order of selection doesn't matter, meaning that the pair {A, B} is the same as {B, A}.
Fi... | [
{
"from": "human",
"value": "Let $S\\,$ be a set with six elements. In how many different ways can one select two not necessarily distinct subsets of $S\\,$ so that the union of the two subsets is $S\\,$? The order of selection does not matter; for example, the pair of subsets $\\{a, c\\},\\{b, c, d, e, f\... |
Given a regular polygon with $n$ sides. It is known that there are $1200$ ways to choose three of the vertices of the polygon such that they form the vertices of a [b]right triangle[/b]. What is the value of $n$? | <think>
Okay, so I need to find the number of sides, n, of a regular polygon where there are 1200 ways to choose three vertices that form a right triangle. Hmm. Let me think about how right triangles can be formed in a regular polygon.
First, in a regular polygon, all sides and angles are equal. A right triangle has o... | [
{
"from": "human",
"value": "Given a regular polygon with $n$ sides. It is known that there are $1200$ ways to choose three of the vertices of the polygon such that they form the vertices of a [b]right triangle[/b]. What is the value of $n$?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I nee... |
1. Let $n$ be a natural number, $a, b$ be positive real numbers, and satisfy the condition $a+b=2$, then the minimum value of $\frac{1}{1+a^{n}}+\frac{1}{1+b^{n}}$ is $\qquad$. | <think>
Alright, so I need to find the minimum value of the expression \(\frac{1}{1+a^{n}} + \frac{1}{1+b^{n}}\) given that \(a\) and \(b\) are positive real numbers with \(a + b = 2\), and \(n\) is a natural number. Hmm, okay. Let me try to break this down step by step.
First, since \(a + b = 2\), maybe I can express... | [
{
"from": "human",
"value": "1. Let $n$ be a natural number, $a, b$ be positive real numbers, and satisfy the condition $a+b=2$, then the minimum value of $\\frac{1}{1+a^{n}}+\\frac{1}{1+b^{n}}$ is $\\qquad$."
},
{
"from": "gpt",
"value": "<think>\nAlright, so I need to find the minimum value of... |
Example 25 Let $x, y, z \in(0,1)$, satisfying:
$$\sqrt{\frac{1-x}{y z}}+\sqrt{\frac{1-y}{z x}}+\sqrt{\frac{1-z}{x y}}=2,$$
Find the maximum value of $x y z$. | <think>
Okay, so I have this problem here: given x, y, z in (0,1), they satisfy the equation
√[(1 - x)/(y z)] + √[(1 - y)/(z x)] + √[(1 - z)/(x y)] = 2,
and I need to find the maximum value of x y z. Hmm, interesting. Let me think about how to approach this.
First, I know that optimization problems with constraints ... | [
{
"from": "human",
"value": "Example 25 Let $x, y, z \\in(0,1)$, satisfying:\n$$\\sqrt{\\frac{1-x}{y z}}+\\sqrt{\\frac{1-y}{z x}}+\\sqrt{\\frac{1-z}{x y}}=2,$$\n\nFind the maximum value of $x y z$."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I have this problem here: given x, y, z in (0,1),... |
146. From a group of 15 people, four participants for the relay race $800+400+200+100$ are selected. In how many ways can the athletes be arranged for the relay stages? | <think>
Okay, so the problem here is: From a group of 15 people, we need to select four participants for a relay race with the stages 800, 400, 200, and 100 meters. The question is asking in how many ways the athletes can be arranged for the relay stages. Hmm, let's see.
First, I need to figure out if this is a permu... | [
{
"from": "human",
"value": "146. From a group of 15 people, four participants for the relay race $800+400+200+100$ are selected. In how many ways can the athletes be arranged for the relay stages?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so the problem here is: From a group of 15 people, w... |
$10 \cdot 10$ Given a four-digit number that satisfies the following conditions:
(1) If the units digit and the hundreds digit, as well as the tens digit and the thousands digit, are simultaneously swapped, then its value increases by 5940;
(2) When divided by 9, the remainder is 8.
Find the smallest odd number among t... | <think>
Okay, let me try to tackle this problem. So, we need to find the smallest four-digit odd number that satisfies two conditions. Let me read them again carefully.
First condition: If we swap the units digit with the hundreds digit, and also swap the tens digit with the thousands digit, the number increases by 59... | [
{
"from": "human",
"value": "$10 \\cdot 10$ Given a four-digit number that satisfies the following conditions:\n(1) If the units digit and the hundreds digit, as well as the tens digit and the thousands digit, are simultaneously swapped, then its value increases by 5940;\n(2) When divided by 9, the remainde... |
4. The area of the figure enclosed by the curve determined by the equation $|x-1|+|y-1|=1$ is
(A) 1
(B) 2
(C) $\pi$
( D ) 4 | <think>
Okay, so I need to find the area enclosed by the curve defined by the equation |x - 1| + |y - 1| = 1. Hmm, let me think. I remember that equations involving absolute values often form shapes like diamonds or squares, especially when you have the sum of two absolute values set equal to a constant.
First, let m... | [
{
"from": "human",
"value": "4. The area of the figure enclosed by the curve determined by the equation $|x-1|+|y-1|=1$ is\n(A) 1\n(B) 2\n(C) $\\pi$\n( D ) 4"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find the area enclosed by the curve defined by the equation |x - 1| + |y - 1| =... |
5. Let the equation
$$
1+x-\frac{x^{2}}{2}+\frac{x^{3}}{3}-\frac{x^{4}}{4}+\cdots-\frac{x^{2018}}{2018}=0
$$
have all its real roots within the interval $[a, b](a, b \in \mathbf{Z}$, $a<b)$. Then the minimum value of $b-a$ is ( ).
(A) 1
(B) 2
(C) 3
(D) 4 | <think>
Okay, so I have this equation here: 1 + x - x²/2 + x³/3 - x⁴/4 + ... - x²⁰¹⁸/2018 = 0. The question is asking for the minimum value of b - a, where all real roots of the equation are within the interval [a, b], and a and b are integers with a < b. The options are 1, 2, 3, or 4. Hmm, let's try to figure this out... | [
{
"from": "human",
"value": "5. Let the equation\n$$\n1+x-\\frac{x^{2}}{2}+\\frac{x^{3}}{3}-\\frac{x^{4}}{4}+\\cdots-\\frac{x^{2018}}{2018}=0\n$$\n\nhave all its real roots within the interval $[a, b](a, b \\in \\mathbf{Z}$, $a<b)$. Then the minimum value of $b-a$ is ( ).\n(A) 1\n(B) 2\n(C) 3\n(D) 4"
},
... |
Let $\mathbb{R}[x]$ be the set of all polynomials with real coefficients. Find all functions $f: \mathbb{R}[x] \rightarrow \mathbb{R}[x]$ satisfying the following conditions:
[list]
[*] $f$ maps the zero polynomial to itself,
[*] for any non-zero polynomial $P \in \mathbb{R}[x]$, $\text{deg} \, f(P) \le 1+ \te... | <think>
Okay, so I need to find all functions f from the real polynomials to themselves that satisfy three conditions. Let me try to parse each condition and see what they imply.
First, f maps the zero polynomial to itself. That's straightforward. So f(0) = 0.
Second, for any non-zero polynomial P, the degree of f(P)... | [
{
"from": "human",
"value": "Let $\\mathbb{R}[x]$ be the set of all polynomials with real coefficients. Find all functions $f: \\mathbb{R}[x] \\rightarrow \\mathbb{R}[x]$ satisfying the following conditions:\n\n[list]\n [*] $f$ maps the zero polynomial to itself,\n [*] for any non-zero polynomial $P \... |
Each face of a [cube](https://artofproblemsolving.com/wiki/index.php/Cube) is painted either red or blue, each with probability $1/2$. The color of each face is determined independently. What is the probability that the painted cube can be placed on a horizontal surface so that the four vertical faces are all the same ... | <think>
Alright, so here's this problem about a cube being painted red or blue on each face, each color with a 1/2 chance, and the colors are determined independently. The question is asking for the probability that the cube can be placed on a horizontal surface such that the four vertical faces are all the same color.... | [
{
"from": "human",
"value": "Each face of a [cube](https://artofproblemsolving.com/wiki/index.php/Cube) is painted either red or blue, each with probability $1/2$. The color of each face is determined independently. What is the probability that the painted cube can be placed on a horizontal surface so that ... |
8. Given six points in space $A, B, C, D, E, F$ with no four points being coplanar. Then the maximum number of line segments that can be drawn so that no tetrahedron exists in the graph is $\qquad$. | <think>
Okay, so I need to find the maximum number of line segments (edges) that can be drawn between six points in space, such that no four points form a tetrahedron. A tetrahedron here means a complete graph K4, right? So, the problem is asking for the largest number of edges in a graph with six vertices that doesn't... | [
{
"from": "human",
"value": "8. Given six points in space $A, B, C, D, E, F$ with no four points being coplanar. Then the maximum number of line segments that can be drawn so that no tetrahedron exists in the graph is $\\qquad$."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find the... |
The following expression is given:
$$
y=x^{2}-(8 a-2) x+15 a^{2}-2 a-7
$$
1. Determine the value of $a$ such that this expression is positive for all values of $a$.
2. Determine the value of $a$ such that the sum of the squares of the roots of the equation $y=0$ is 24. | <think>
Okay, let's see. I need to solve two parts of this problem. The first part is to find the value of 'a' such that the quadratic expression y is positive for all values of x. The second part is to find the value of 'a' such that the sum of the squares of the roots of y=0 is 24. Let me start with the first part.
... | [
{
"from": "human",
"value": "The following expression is given:\n\n$$\ny=x^{2}-(8 a-2) x+15 a^{2}-2 a-7\n$$\n\n1. Determine the value of $a$ such that this expression is positive for all values of $a$.\n2. Determine the value of $a$ such that the sum of the squares of the roots of the equation $y=0$ is 24."... |
$23 \cdot 31$ In the cube $A B C D-A_{1} B_{1} C_{1} D_{1}$, $P, M, N$ are the midpoints of edges $A A_{1}$, $B C, C C_{1}$ respectively. The figure formed by the intersection lines of the plane determined by these three points with the surface of the cube is
(A) a rhombus.
(B) a regular pentagon.
(C) a regular hexagon... | <think>
Okay, let me try to figure out this geometry problem. So, we have a cube labeled ABCD-A₁B₁C₁D₁. Points P, M, N are the midpoints of edges AA₁, BC, and CC₁ respectively. We need to find the shape formed by the intersection lines of the plane determined by these three points with the surface of the cube. The opti... | [
{
"from": "human",
"value": "$23 \\cdot 31$ In the cube $A B C D-A_{1} B_{1} C_{1} D_{1}$, $P, M, N$ are the midpoints of edges $A A_{1}$, $B C, C C_{1}$ respectively. The figure formed by the intersection lines of the plane determined by these three points with the surface of the cube is\n(A) a rhombus.\n(... |
7.1. The sum of the minuend, subtrahend, and difference is 25. Find the minuend. | <think>
Okay, so I need to solve this problem where the sum of the minuend, subtrahend, and difference is 25, and I have to find the minuend. Hmm, let me start by recalling what those terms mean.
In subtraction, the minuend is the number you start with, the subtrahend is the number you subtract from it, and the diffe... | [
{
"from": "human",
"value": "7.1. The sum of the minuend, subtrahend, and difference is 25. Find the minuend."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to solve this problem where the sum of the minuend, subtrahend, and difference is 25, and I have to find the minuend. Hmm, let me ... |
12. A piggy bank contains 24 coins, all nickels, dimes, and quarters. If the total value of the coins is two dollars, what combinations of coins are possible? | <think>
Okay, so I need to figure out the possible combinations of nickels, dimes, and quarters in a piggy bank that has 24 coins totaling two dollars. Hmm, let me start by setting up some equations.
Let me denote the number of nickels as N, dimes as D, and quarters as Q. Then, according to the problem, the total num... | [
{
"from": "human",
"value": "12. A piggy bank contains 24 coins, all nickels, dimes, and quarters. If the total value of the coins is two dollars, what combinations of coins are possible?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to figure out the possible combinations of nickels, ... |
Let's divide 17 into two parts such that $3/4$ of one part is $a$ greater than $5/6$ of the other part, where $a>0$. What are the limits within which the value of $a$ can vary to ensure that the problem is always solvable? | <think>
Okay, let me try to figure out this problem. So, the task is to divide 17 into two parts such that 3/4 of one part is greater than 5/6 of the other part by some positive number a. And we need to find the limits within which a can vary so that the problem is always solvable. Hmm, let's break it down step by step... | [
{
"from": "human",
"value": "Let's divide 17 into two parts such that $3/4$ of one part is $a$ greater than $5/6$ of the other part, where $a>0$. What are the limits within which the value of $a$ can vary to ensure that the problem is always solvable?"
},
{
"from": "gpt",
"value": "<think>\nOkay... |
12.129. Find the volume of a regular quadrilateral pyramid if the side of its base is equal to $a$, and the dihedral angle at the base is $\alpha$. | <think>
Okay, so I need to find the volume of a regular quadrilateral pyramid where the base has side length 'a' and the dihedral angle at the base is α. Let me start by recalling the formula for the volume of a pyramid. Volume is (1/3) times the area of the base times the height. The base here is a square with side le... | [
{
"from": "human",
"value": "12.129. Find the volume of a regular quadrilateral pyramid if the side of its base is equal to $a$, and the dihedral angle at the base is $\\alpha$."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find the volume of a regular quadrilateral pyramid where th... |
Prove that for all real $x > 0$ holds the inequality $$\sqrt{\frac{1}{3x+1}}+\sqrt{\frac{x}{x+3}}\ge 1.$$
For what values of $x$ does the equality hold? | <think>
Alright, so I need to prove that for all real numbers x > 0, the inequality √(1/(3x + 1)) + √(x/(x + 3)) ≥ 1 holds. Also, I have to find the values of x where equality occurs. Hmm, okay. Let me start by understanding the problem and thinking about possible approaches.
First, since x is positive, all the denomi... | [
{
"from": "human",
"value": "Prove that for all real $x > 0$ holds the inequality $$\\sqrt{\\frac{1}{3x+1}}+\\sqrt{\\frac{x}{x+3}}\\ge 1.$$\nFor what values of $x$ does the equality hold?"
},
{
"from": "gpt",
"value": "<think>\nAlright, so I need to prove that for all real numbers x > 0, the ine... |
(3) Given 5 different real numbers, taking any two to find their sum yields 10 sum values, among which the smallest three sums are $32, 36, 37$, and the largest two sums are 48 and 51, then the largest number among these 5 numbers is equal to | <think>
Okay, so I have this problem here with five different real numbers. When you take any two and add them, you get 10 sums. Out of these, the smallest three are 32, 36, and 37, and the largest two are 48 and 51. The question is asking for the largest number among these five. Hmm, let me think about how to approach... | [
{
"from": "human",
"value": "(3) Given 5 different real numbers, taking any two to find their sum yields 10 sum values, among which the smallest three sums are $32, 36, 37$, and the largest two sums are 48 and 51, then the largest number among these 5 numbers is equal to"
},
{
"from": "gpt",
"va... |
12.309. The base of the prism is a rectangle. The lateral edge forms equal angles with the sides of the base and is inclined to the plane of the base at an angle $\alpha$. Find the angle between the lateral edge and the side of the base. | <think>
Okay, so I need to find the angle between the lateral edge of a prism and the side of the base. The base is a rectangle, and the lateral edge forms equal angles with the sides of the base. Also, the lateral edge is inclined to the plane of the base at an angle α. Hmm, let me try to visualize this.
First, let m... | [
{
"from": "human",
"value": "12.309. The base of the prism is a rectangle. The lateral edge forms equal angles with the sides of the base and is inclined to the plane of the base at an angle $\\alpha$. Find the angle between the lateral edge and the side of the base."
},
{
"from": "gpt",
"value"... |
If $T_n=1+2+3+\cdots +n$ and
\[P_n=\frac{T_2}{T_2-1}\cdot\frac{T_3}{T_3-1}\cdot\frac{T_4}{T_4-1}\cdot\cdots\cdot\frac{T_n}{T_n-1}\]
for $n=2,3,4,\cdots,$ then $P_{1991}$ is closest to which of the following numbers?
$\text{(A) } 2.0\quad \text{(B) } 2.3\quad \text{(C) } 2.6\quad \text{(D) } 2.9\quad \text{(E) } 3.2$ | <think>
Okay, let's try to figure out this problem. So, we have T_n which is the nth triangular number, right? That means T_n = 1 + 2 + 3 + ... + n. I remember the formula for triangular numbers is T_n = n(n + 1)/2. Let me check that. Yeah, for example, T_2 should be 1 + 2 = 3, and plugging into the formula: 2(3)/2 = 3... | [
{
"from": "human",
"value": "If $T_n=1+2+3+\\cdots +n$ and\n\\[P_n=\\frac{T_2}{T_2-1}\\cdot\\frac{T_3}{T_3-1}\\cdot\\frac{T_4}{T_4-1}\\cdot\\cdots\\cdot\\frac{T_n}{T_n-1}\\]\nfor $n=2,3,4,\\cdots,$ then $P_{1991}$ is closest to which of the following numbers?\n$\\text{(A) } 2.0\\quad \\text{(B) } 2.3\\quad ... |
6. [25] Into how many regions can a circle be cut by 10 parabolas? | <think>
Okay, so the problem is: Into how many regions can a circle be cut by 10 parabolas? Hmm, interesting. I remember that similar problems involve finding the maximum number of regions created by intersecting lines or other curves. For example, with lines, the formula is n(n+1)/2 +1. But parabolas are different. Le... | [
{
"from": "human",
"value": "6. [25] Into how many regions can a circle be cut by 10 parabolas?"
},
{
"from": "gpt",
"value": "<think>\nOkay, so the problem is: Into how many regions can a circle be cut by 10 parabolas? Hmm, interesting. I remember that similar problems involve finding the maxim... |
3. Given the complex sequence $\left\{a_{n}\right\}$ with the general term $a_{n}=(1+\mathrm{i}) \cdot\left(1+\frac{\mathrm{i}}{\sqrt{2}}\right) \cdots\left(1+\frac{\mathrm{i}}{\sqrt{n}}\right)$, then $\left|a_{n}-a_{n+1}\right|=$ | <think>
Okay, so I need to find the absolute value of the difference between consecutive terms of this complex sequence. The sequence is defined as a product of terms each of the form (1 + i/√k) starting from k=1 up to n. Specifically, the general term is a_n = (1 + i) * (1 + i/√2) * ... * (1 + i/√n). Then, we have to ... | [
{
"from": "human",
"value": "3. Given the complex sequence $\\left\\{a_{n}\\right\\}$ with the general term $a_{n}=(1+\\mathrm{i}) \\cdot\\left(1+\\frac{\\mathrm{i}}{\\sqrt{2}}\\right) \\cdots\\left(1+\\frac{\\mathrm{i}}{\\sqrt{n}}\\right)$, then $\\left|a_{n}-a_{n+1}\\right|=$"
},
{
"from": "gpt",
... |
## Problem Statement
Find the indefinite integral:
$$
\int \frac{\sqrt{1+\sqrt[3]{x}}}{x \sqrt{x}} d x
$$ | <think>
Okay, let's see... I need to find the indefinite integral of sqrt(1 + cube root(x)) divided by x times sqrt(x). Hmm, first, I should probably simplify the expression in the integrand to make it easier to work with. Let me write down the integral again:
∫ [sqrt(1 + ∛x)] / [x * sqrt(x)] dx
Wait, the denominator... | [
{
"from": "human",
"value": "## Problem Statement\n\nFind the indefinite integral:\n\n$$\n\\int \\frac{\\sqrt{1+\\sqrt[3]{x}}}{x \\sqrt{x}} d x\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see... I need to find the indefinite integral of sqrt(1 + cube root(x)) divided by x times sqrt(... |
13. Determine the maximum positive integer $k$ such that $k^{2}$ divides $\frac{n !}{(n-6) !}$ for every $n>6$.
| <think>
Okay, so I need to figure out the maximum positive integer k such that k squared divides n! divided by (n-6)! for every n greater than 6. Hmm, let me start by understanding the problem.
First, the expression n!/(n-6)! is equal to the product of 6 consecutive integers: n(n-1)(n-2)(n-3)(n-4)(n-5). So, essentiall... | [
{
"from": "human",
"value": "13. Determine the maximum positive integer $k$ such that $k^{2}$ divides $\\frac{n !}{(n-6) !}$ for every $n>6$.\n\n"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to figure out the maximum positive integer k such that k squared divides n! divided by (n-6)! ... |
7. Given positive real numbers $a, b$ satisfy $a b(a+b)=4$, then the minimum value of $2 a+b$ is $\qquad$
Translate the above text into English, please keep the original text's line breaks and format, and output the translation result directly. | <think>
Alright, let's tackle this problem. We have positive real numbers a and b that satisfy the equation ab(a + b) = 4. We need to find the minimum value of 2a + b.
First, I should recall some optimization techniques. Since there's a constraint given by ab(a + b) = 4, maybe I can use the method of Lagrange multipli... | [
{
"from": "human",
"value": "7. Given positive real numbers $a, b$ satisfy $a b(a+b)=4$, then the minimum value of $2 a+b$ is $\\qquad$\n\nTranslate the above text into English, please keep the original text's line breaks and format, and output the translation result directly."
},
{
"from": "gpt",
... |
Example 1 Add a “+” or “-” in front of each number in $1,2, \cdots, 1989$. Find the minimum non-negative algebraic sum, and write down the equation. | <think>
Okay, let me try to work through this problem. So, the task is to add a "+" or "-" in front of each number from 1 to 1989, and we need to find the minimum non-negative algebraic sum possible. Then, we have to write down the equation that gives this sum. Hmm, interesting. Let me break this down step by step.
Fi... | [
{
"from": "human",
"value": "Example 1 Add a “+” or “-” in front of each number in $1,2, \\cdots, 1989$. Find the minimum non-negative algebraic sum, and write down the equation."
},
{
"from": "gpt",
"value": "<think>\nOkay, let me try to work through this problem. So, the task is to add a \"+\"... |
10. (20 points) In the sequence $\left\{a_{n}\right\}$, let $S_{n}=\sum_{i=1}^{n} a_{i}$ $\left(n \in \mathbf{Z}_{+}\right)$, with the convention: $S_{0}=0$. It is known that
$$
a_{k}=\left\{\begin{array}{ll}
k, & S_{k-1}<k ; \\
-k, & S_{k-1} \geqslant k
\end{array}\left(1 \leqslant k \leqslant n, k 、 n \in \mathbf{Z}_... | <think>
Alright, so I have this problem here where I need to find the largest positive integer n, not exceeding 2019, such that S_n = 0. The sequence {a_n} is defined in a particular way based on the previous sum S_{k-1}. Let me try to unpack this step by step.
First, the problem defines S_n as the sum of the first n ... | [
{
"from": "human",
"value": "10. (20 points) In the sequence $\\left\\{a_{n}\\right\\}$, let $S_{n}=\\sum_{i=1}^{n} a_{i}$ $\\left(n \\in \\mathbf{Z}_{+}\\right)$, with the convention: $S_{0}=0$. It is known that\n$$\na_{k}=\\left\\{\\begin{array}{ll}\nk, & S_{k-1}<k ; \\\\\n-k, & S_{k-1} \\geqslant k\n\\en... |
9.48 The total weight of a pile of stones is 100 kilograms, where the weight of each stone does not exceed 2 kilograms. By taking out some of the stones in various ways and calculating the difference between the sum of the weights of these stones and 10 kilograms. Among all these differences, the minimum value of their... | <think>
Alright, so I need to solve this problem where there's a pile of stones totaling 100 kilograms, each stone is at most 2 kilograms. The goal is to find the maximum possible minimum difference 'd' when trying to take out some stones such that their total weight is as close as possible to 10 kilograms. Essentially... | [
{
"from": "human",
"value": "9.48 The total weight of a pile of stones is 100 kilograms, where the weight of each stone does not exceed 2 kilograms. By taking out some of the stones in various ways and calculating the difference between the sum of the weights of these stones and 10 kilograms. Among all thes... |
14.5.13 ** Find the smallest positive integer $n$ (where $n>1$) such that the square mean of the first $n$ natural numbers is an integer. | <think>
Okay, so I need to find the smallest positive integer n greater than 1 such that the square mean of the first n natural numbers is an integer. Hmm, let me start by understanding what exactly the "square mean" means here. I remember that there are different kinds of means—like arithmetic mean, geometric mean, ha... | [
{
"from": "human",
"value": "14.5.13 ** Find the smallest positive integer $n$ (where $n>1$) such that the square mean of the first $n$ natural numbers is an integer."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find the smallest positive integer n greater than 1 such that the squa... |
Example 6 Let $x y=1$, and $x>y>0$, find the minimum value of $\frac{x^{2}+y^{2}}{x-y}$.
untranslated text is retained in its original form. | <think>
Okay, so I need to find the minimum value of the expression (x² + y²)/(x - y) given that xy = 1 and x is greater than y, which is greater than 0. Hmm, let's see. First, maybe I can express one variable in terms of the other using the constraint xy = 1. That way, I can reduce the problem to a single variable opt... | [
{
"from": "human",
"value": "Example 6 Let $x y=1$, and $x>y>0$, find the minimum value of $\\frac{x^{2}+y^{2}}{x-y}$.\n\n untranslated text is retained in its original form."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find the minimum value of the expression (x² + y²)/(x - y) giv... |
Example 6 Solve the system of equations in the real numbers
$$
\left\{\begin{array}{l}
x y+y z+z x=1, \\
5\left(x+\frac{1}{x}\right)=12\left(y+\frac{1}{y}\right)=13\left(z+\frac{1}{z}\right) .
\end{array}\right.
$$ | <think>
Alright, let's tackle this system of equations. Hmm, okay, we have three variables: x, y, z. The first equation is xy + yz + zx = 1. The second part is a bit more complex: 5(x + 1/x) = 12(y + 1/y) = 13(z + 1/z). So, it's like three expressions set equal to each other. Let me break this down step by step.
First... | [
{
"from": "human",
"value": "Example 6 Solve the system of equations in the real numbers\n$$\n\\left\\{\\begin{array}{l}\nx y+y z+z x=1, \\\\\n5\\left(x+\\frac{1}{x}\\right)=12\\left(y+\\frac{1}{y}\\right)=13\\left(z+\\frac{1}{z}\\right) .\n\\end{array}\\right.\n$$"
},
{
"from": "gpt",
"value": ... |
7. Let $A_{1}$ and $A_{2}$ be the left and right vertices of the ellipse $\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1(a>b>0)$. If there exists a point $P$ on the ellipse, different from $A_{1}$ and $A_{2}$, such that $\overrightarrow{P O} \cdot \overrightarrow{P A_{2}}=0$, where $O$ is the origin, then the range of the e... | <think>
Okay, so I need to solve this problem about the eccentricity of an ellipse. Let me first recall what the question is asking. The ellipse is given by the equation x²/a² + y²/b² = 1, where a > b > 0. The points A₁ and A₂ are the left and right vertices, so their coordinates should be (-a, 0) and (a, 0) respective... | [
{
"from": "human",
"value": "7. Let $A_{1}$ and $A_{2}$ be the left and right vertices of the ellipse $\\frac{x^{2}}{a^{2}}+\\frac{y^{2}}{b^{2}}=1(a>b>0)$. If there exists a point $P$ on the ellipse, different from $A_{1}$ and $A_{2}$, such that $\\overrightarrow{P O} \\cdot \\overrightarrow{P A_{2}}=0$, wh... |
Example X (China Mathematical Olympiad 2000) Given that $a, b, c$ are the sides of $\triangle ABC$, $a \leqslant b \leqslant c$, and $R$ and $r$ are the radii of the circumcircle and incircle of $\triangle ABC$, respectively. Let $f=a+b-2 R-2 r$, try to determine the sign of $f$ using the size of angle $C$.
| <think>
Okay, let's try to figure out this problem. So, we have a triangle ABC with sides a, b, c, where a ≤ b ≤ c. We know that in a triangle, the larger side is opposite the larger angle. Since a ≤ b ≤ c, that means angle A ≤ angle B ≤ angle C. So angle C is the largest angle. The problem is asking us to determine th... | [
{
"from": "human",
"value": "Example X (China Mathematical Olympiad 2000) Given that $a, b, c$ are the sides of $\\triangle ABC$, $a \\leqslant b \\leqslant c$, and $R$ and $r$ are the radii of the circumcircle and incircle of $\\triangle ABC$, respectively. Let $f=a+b-2 R-2 r$, try to determine the sign of... |
9. (15 points) As shown in Figure 2, circle $\odot M$ is externally tangent to circle $\odot O$ at point $C$, with radii $r$ and $R$ for $\odot M$ and $\odot O$ respectively. Line $TPQ$ is tangent to $\odot M$ at point $T$, and intersects $\odot O$ at points $P$ and $Q$. Find the value of $\frac{CQ - CP}{PQ}$. | <think>
Okay, so I have this geometry problem here. Let me try to visualize it first. There are two circles, circle M and circle O. They're externally tangent at point C. The radius of circle M is r, and the radius of circle O is R. There's a line called TPQ that's tangent to circle M at point T, and this line intersec... | [
{
"from": "human",
"value": "9. (15 points) As shown in Figure 2, circle $\\odot M$ is externally tangent to circle $\\odot O$ at point $C$, with radii $r$ and $R$ for $\\odot M$ and $\\odot O$ respectively. Line $TPQ$ is tangent to $\\odot M$ at point $T$, and intersects $\\odot O$ at points $P$ and $Q$. F... |
6. Given point $P$ is in the plane of Rt $\triangle A B C$, $\angle B A C=90^{\circ}, \angle C A P$ is an acute angle, and
$|\overrightarrow{A P}|=2, \overrightarrow{A P} \cdot \overrightarrow{A C}=2, \overrightarrow{A P} \cdot \overrightarrow{A B}=1$.
When $| \overrightarrow{A B}+\overrightarrow{A C}+\overrightarrow{A... | <think>
Okay, so I need to find the value of tan(angle CAP) when the magnitude of the vector AB + AC + AP is minimized. Let me try to visualize the problem first.
We have a right triangle ABC with a right angle at A. Point P is somewhere in the plane of this triangle. The angle CAP is acute, and the length of vector A... | [
{
"from": "human",
"value": "6. Given point $P$ is in the plane of Rt $\\triangle A B C$, $\\angle B A C=90^{\\circ}, \\angle C A P$ is an acute angle, and\n$|\\overrightarrow{A P}|=2, \\overrightarrow{A P} \\cdot \\overrightarrow{A C}=2, \\overrightarrow{A P} \\cdot \\overrightarrow{A B}=1$.\nWhen $| \\ove... |
2 Find all integer $x$ such that $\left|4 x^{2}-12 x-27\right|$ is a prime number.
Find all integer $x$ such that $\left|4 x^{2}-12 x-27\right|$ is a prime number. | <think>
Okay, so I need to find all integer values of x such that the absolute value of the quadratic expression 4x² - 12x - 27 is a prime number. Hmm, let's start by understanding the problem step by step.
First, the expression inside the absolute value is 4x² - 12x - 27. Since we have an absolute value, the result w... | [
{
"from": "human",
"value": "2 Find all integer $x$ such that $\\left|4 x^{2}-12 x-27\\right|$ is a prime number.\n\nFind all integer $x$ such that $\\left|4 x^{2}-12 x-27\\right|$ is a prime number."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find all integer values of x such tha... |
10.13 A nine-digit number in the form $\overline{a_{1} a_{2} a_{3} b_{1} b_{2} b_{3} a_{1} a_{2} a_{3}}$ is equal to the square of the product of 5 prime numbers, and $\overline{b_{1} b_{2} b_{3}}=2 \overline{a_{1} a_{2} a_{3}} \quad\left(a_{1} \neq 0\right)$. Find this nine-digit number.
(China Shaanxi Province Mathem... | <think>
Okay, let's try to solve this problem step by step. The problem is about finding a nine-digit number with a specific structure. The number is in the form \(\overline{a_{1} a_{2} a_{3} b_{1} b_{2} b_{3} a_{1} a_{2} a_{3}}}\), which means the first three digits are \(a_1a_2a_3\), the next three digits are \(b_1b_... | [
{
"from": "human",
"value": "10.13 A nine-digit number in the form $\\overline{a_{1} a_{2} a_{3} b_{1} b_{2} b_{3} a_{1} a_{2} a_{3}}$ is equal to the square of the product of 5 prime numbers, and $\\overline{b_{1} b_{2} b_{3}}=2 \\overline{a_{1} a_{2} a_{3}} \\quad\\left(a_{1} \\neq 0\\right)$. Find this n... |
4. [6] Let $A B C D$ be a square of side length 2. Let points $X, Y$, and $Z$ be constructed inside $A B C D$ such that $A B X, B C Y$, and $C D Z$ are equilateral triangles. Let point $W$ be outside $A B C D$ such that triangle $D A W$ is equilateral. Let the area of quadrilateral $W X Y Z$ be $a+\sqrt{b}$, where $a$ ... | <think>
Okay, so I need to solve this geometry problem involving a square ABCD with side length 2. There are equilateral triangles ABX, BCY, CDZ inside the square, and another equilateral triangle DAW outside the square. Then, I have to find the area of quadrilateral WXYZ, which is given in the form a + √b, and compute... | [
{
"from": "human",
"value": "4. [6] Let $A B C D$ be a square of side length 2. Let points $X, Y$, and $Z$ be constructed inside $A B C D$ such that $A B X, B C Y$, and $C D Z$ are equilateral triangles. Let point $W$ be outside $A B C D$ such that triangle $D A W$ is equilateral. Let the area of quadrilate... |
One. (20 points) Determine for which positive integers $a$, the equation
$$
5 x^{2}-4(a+3) x+a^{2}-29=0
$$
has positive integer solutions? And find all positive integer solutions of the equation. | <think>
Okay, so I need to figure out for which positive integers \( a \) the quadratic equation \( 5x^2 - 4(a + 3)x + a^2 - 29 = 0 \) has positive integer solutions. Then, I also have to find all those solutions. Hmm, let's start by recalling that for a quadratic equation \( Ax^2 + Bx + C = 0 \), the solutions can be ... | [
{
"from": "human",
"value": "One. (20 points) Determine for which positive integers $a$, the equation\n$$\n5 x^{2}-4(a+3) x+a^{2}-29=0\n$$\n\nhas positive integer solutions? And find all positive integer solutions of the equation."
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to figure... |
Problem 3. Determine all real values of $(x, y, z)$ for which
$$
\begin{array}{cccc}
x+y+z & = & 1 \\
x^{2} y+y^{2} z+z^{2} x & = & x y^{2}+y z^{2}+z x^{2} \\
x^{3}+y^{2}+z & = & y^{3}+z^{2}+x
\end{array}
$$ | <think>
Okay, so I need to solve this system of equations with three variables: x, y, z. Let me write them down again to make sure I have them right.
First equation: x + y + z = 1
Second equation: x²y + y²z + z²x = xy² + yz² + zx²
Third equation: x³ + y² + z = y³ + z² + x
Hmm, these look a bit complicated. Let me s... | [
{
"from": "human",
"value": "Problem 3. Determine all real values of $(x, y, z)$ for which\n\n$$\n\\begin{array}{cccc}\nx+y+z & = & 1 \\\\\nx^{2} y+y^{2} z+z^{2} x & = & x y^{2}+y z^{2}+z x^{2} \\\\\nx^{3}+y^{2}+z & = & y^{3}+z^{2}+x\n\\end{array}\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay... |
SUBIECTUL III
Let point O be the midpoint of a straight segment $[A B]$. On the ray (OA, consider a point $\mathrm{E}$ such that $B E=5 \cdot A E$. Find the length of the segment $A B$ knowing that $E O=6 \mathrm{~cm}$. | <think>
Okay, let me try to solve this geometry problem. Let's start by understanding what's given and what we need to find.
First, we have a straight segment AB, and O is the midpoint of AB. That means AO = OB. Then, on the ray OA (which starts at O and goes through A, right?), there's a point E such that BE = 5 * AE... | [
{
"from": "human",
"value": "SUBIECTUL III\n\nLet point O be the midpoint of a straight segment $[A B]$. On the ray (OA, consider a point $\\mathrm{E}$ such that $B E=5 \\cdot A E$. Find the length of the segment $A B$ knowing that $E O=6 \\mathrm{~cm}$."
},
{
"from": "gpt",
"value": "<think>\nO... |
13. Define $n!=1 \times 2 \times \ldots \times n$, for example, $5!=1 \times 2 \times 3 \times 4 \times 5$. If $\frac{n! \times (n+1)!}{2}$ (where $\mathbf{n}$ is a positive integer, and $1 \leq n \leq 100$) is a perfect square, for example, when $n=7$, $\frac{n! \times (n+1)!}{2}=\frac{7 \times (7+1)!}{2}=\frac{7 \tim... | <think>
Okay, let's see. The problem says that for a positive integer n between 1 and 100, the expression (n! × (n+1)!)/2 is a perfect square. We need to find all such n and sum them up. The example given is n=7, where the expression simplifies to (7!)^2 × 2^2, which is a perfect square. So, the task is to figure out w... | [
{
"from": "human",
"value": "13. Define $n!=1 \\times 2 \\times \\ldots \\times n$, for example, $5!=1 \\times 2 \\times 3 \\times 4 \\times 5$. If $\\frac{n! \\times (n+1)!}{2}$ (where $\\mathbf{n}$ is a positive integer, and $1 \\leq n \\leq 100$) is a perfect square, for example, when $n=7$, $\\frac{n! \... |
In a bag, there are 8 balls, labeled from 1 to 8. After stirring these 8 balls sufficiently, two balls are drawn from the bag at a time. Let denote $ S$ the sum of the two balls.
(1) Find the probability such that $ S$ doesn't exceed in eight.
(2) Let $ f(n)$ be the probability such that $ S$ takes value $ n$. Fi... | <think>
Okay, let's try to solve these probability problems step by step. So, we have a bag with 8 balls labeled 1 to 8. We need to draw two balls at a time and consider their sum, S.
Starting with part (1): Find the probability that S doesn't exceed eight. Hmm, so we need all pairs of two balls where their sum is 8 ... | [
{
"from": "human",
"value": "In a bag, there are 8 balls, labeled from 1 to 8. After stirring these 8 balls sufficiently, two balls are drawn from the bag at a time. Let denote $ S$ the sum of the two balls.\r\n\r\n(1) Find the probability such that $ S$ doesn't exceed in eight.\r\n\r\n(2) Let $ f(n)$ be th... |
B4. A sheet of paper has the shape of a rectangle with sides measuring $12.6 \mathrm{~cm}$ and $10 \mathrm{~cm}$.
a) This sheet is rolled into the mantle of a cylinder such that the shorter side of the rectangle is the height of the cylinder. Calculate the volume of the cylinder formed by this rolled paper, accurate t... | <think>
Okay, let's tackle part a) first. So the problem is about rolling a rectangular sheet of paper into a cylinder's mantle. The rectangle has sides 12.6 cm and 10 cm. They specify that the shorter side (which is 10 cm) is the height of the cylinder. So I need to find the volume of this cylinder, accurate to the ne... | [
{
"from": "human",
"value": "B4. A sheet of paper has the shape of a rectangle with sides measuring $12.6 \\mathrm{~cm}$ and $10 \\mathrm{~cm}$.\n\na) This sheet is rolled into the mantle of a cylinder such that the shorter side of the rectangle is the height of the cylinder. Calculate the volume of the cyl... |
For arbiterary integers $n,$ find the continuous function $f(x)$ which satisfies the following equation. \[\lim_{h\rightarrow 0}\frac{1}{h}\int_{x-nh}^{x+nh}f(t) dt=2f(nx).\] Note that $x$ can range all real numbers and $f(1)=1.$ | <think>
Okay, so I need to find a continuous function f(x) that satisfies this equation for any integer n:
\[
\lim_{h\rightarrow 0}\frac{1}{h}\int_{x-nh}^{x+nh}f(t) dt=2f(nx).
\]
And also, f(1) = 1. Alright, let me start by understanding what this equation is saying. The left side is the limit as h approaches 0 of th... | [
{
"from": "human",
"value": "For arbiterary integers $n,$ find the continuous function $f(x)$ which satisfies the following equation. \\[\\lim_{h\\rightarrow 0}\\frac{1}{h}\\int_{x-nh}^{x+nh}f(t) dt=2f(nx).\\] Note that $x$ can range all real numbers and $f(1)=1.$"
},
{
"from": "gpt",
"value": "... |
2. If $a^{2}+a+1=0$, determine the value of the expression
$$
a^{1987}+\frac{1}{a^{1987}}
$$ | <think>
Okay, let's see. I have this equation a² + a + 1 = 0, and I need to find the value of a¹⁹⁸⁷ + 1/a¹⁹⁸⁷. Hmm, that exponent is really big, 1987. I need to figure out a pattern or maybe use some properties of roots of this equation. Let me start by understanding the given equation first.
So, the equation is a qua... | [
{
"from": "human",
"value": "2. If $a^{2}+a+1=0$, determine the value of the expression\n\n$$\na^{1987}+\\frac{1}{a^{1987}}\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. I have this equation a² + a + 1 = 0, and I need to find the value of a¹⁹⁸⁷ + 1/a¹⁹⁸⁷. Hmm, that exponent is rea... |
8.2. One side of the rectangle (width) was increased by $10 \%$, and the other (length) - by $20 \%$. a) Could the perimeter increase by more than 20\%? b) Find the ratio of the sides of the original rectangle if it is known that the perimeter of the new rectangle is $18 \%$ larger than the perimeter of the original? | <think>
Okay, so I've got this problem about a rectangle where one side is increased by 10% and the other by 20%. Part a asks if the perimeter could increase by more than 20%. Hmm. Let me think about how perimeters work.
First, the perimeter of a rectangle is calculated as P = 2*(length + width). So, if both sides ar... | [
{
"from": "human",
"value": "8.2. One side of the rectangle (width) was increased by $10 \\%$, and the other (length) - by $20 \\%$. a) Could the perimeter increase by more than 20\\%? b) Find the ratio of the sides of the original rectangle if it is known that the perimeter of the new rectangle is $18 \\%$... |
4. The range of the function $y=x+\sqrt{x^{2}-3 x+2}$ is | <think>
Okay, let's see. I need to find the range of the function y = x + sqrt(x² - 3x + 2). Hmm, the range means all the possible values that y can take. To do this, I probably need to figure out the domain of the function first because the square root has to be defined. So, the expression under the square root, which... | [
{
"from": "human",
"value": "4. The range of the function $y=x+\\sqrt{x^{2}-3 x+2}$ is"
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. I need to find the range of the function y = x + sqrt(x² - 3x + 2). Hmm, the range means all the possible values that y can take. To do this, I probably... |
Determine all pairs $(x, y)$ of integers satisfying $x^{2}=y^{2}\left(x+y^{4}+2 y^{2}\right)$ | <think>
Okay, so I need to find all integer pairs (x, y) that satisfy the equation x² = y²(x + y⁴ + 2y²). Hmm, let's start by trying to understand this equation better. Maybe I can rearrange it or factor it somehow. Let's write it out again:
x² = y²(x + y⁴ + 2y²)
First, let me see if I can simplify the right-hand sid... | [
{
"from": "human",
"value": "Determine all pairs $(x, y)$ of integers satisfying $x^{2}=y^{2}\\left(x+y^{4}+2 y^{2}\\right)$"
},
{
"from": "gpt",
"value": "<think>\nOkay, so I need to find all integer pairs (x, y) that satisfy the equation x² = y²(x + y⁴ + 2y²). Hmm, let's start by trying to und... |
2 Points $A, B, C, D$ in space satisfy $|\overrightarrow{A B}|=3,|\overrightarrow{B C}|=7$, $|\overrightarrow{C D}|=11,|\overrightarrow{D A}|=9$, then the value of $\overrightarrow{A C} \cdot \overrightarrow{B D}$ is ( ).
(A) only one
(B) two
(C) four
(D) infinitely many | <think>
Okay, let's see. The problem is about four points A, B, C, D in space with the lengths of the vectors AB, BC, CD, and DA given as 3, 7, 11, and 9 respectively. We need to find the value of the dot product of vectors AC and BD. The options are (A) only one, (B) two, (C) four, (D) infinitely many. Hmm, so they're... | [
{
"from": "human",
"value": "2 Points $A, B, C, D$ in space satisfy $|\\overrightarrow{A B}|=3,|\\overrightarrow{B C}|=7$, $|\\overrightarrow{C D}|=11,|\\overrightarrow{D A}|=9$, then the value of $\\overrightarrow{A C} \\cdot \\overrightarrow{B D}$ is ( ).\n(A) only one\n(B) two\n(C) four\n(D) infinitely m... |
1.7 density, 400 gr weight liquid is mixed with 1.2 density $600 \mathrm{gr}$ solution. Measuring the density $D$ of the newly formed solution, we find that $D=1.4$. What is the contraction that occurs when mixing the two initial liquids? | <think>
Okay, so I need to figure out the contraction that happened when mixing these two liquids. Let me start by understanding the problem again. We have two liquids: one with a density of 1.7 g/cm³ and a weight of 400 grams, and another with a density of 1.2 g/cm³ and a weight of 600 grams. When they're mixed, the r... | [
{
"from": "human",
"value": "1.7 density, 400 gr weight liquid is mixed with 1.2 density $600 \\mathrm{gr}$ solution. Measuring the density $D$ of the newly formed solution, we find that $D=1.4$. What is the contraction that occurs when mixing the two initial liquids?"
},
{
"from": "gpt",
"value... |
Example 8 Find the value of $\cos ^{5} \frac{\pi}{9}+\cos ^{5} \frac{5 \pi}{9}+\cos ^{5} \frac{7 \pi}{9}$. | <think>
Okay, let's see. The problem is to find the value of cos⁵(π/9) + cos⁵(5π/9) + cos⁵(7π/9). Hmm, fifth powers of cosines at specific angles. That seems a bit complicated. I need to recall some trigonometric identities or maybe some strategies to simplify such expressions.
First, maybe I can express cos⁵θ in term... | [
{
"from": "human",
"value": "Example 8 Find the value of $\\cos ^{5} \\frac{\\pi}{9}+\\cos ^{5} \\frac{5 \\pi}{9}+\\cos ^{5} \\frac{7 \\pi}{9}$."
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. The problem is to find the value of cos⁵(π/9) + cos⁵(5π/9) + cos⁵(7π/9). Hmm, fifth powers of ... |
Zaslavsky A.A.
Let $O, I$ be the centers of the circumcircle and incircle of a right triangle; $R, r$ be the radii of these circles; $J$ be the point symmetric to the right-angle vertex with respect to $I$. Find $O J$. | <think>
Okay, so I have this geometry problem here about a right triangle. The centers of the circumcircle and incircle are O and I, respectively, with radii R and r. There's also a point J, which is the symmetric point to the right-angle vertex with respect to I. I need to find the distance OJ. Hmm, let's break this d... | [
{
"from": "human",
"value": "Zaslavsky A.A.\n\nLet $O, I$ be the centers of the circumcircle and incircle of a right triangle; $R, r$ be the radii of these circles; $J$ be the point symmetric to the right-angle vertex with respect to $I$. Find $O J$."
},
{
"from": "gpt",
"value": "<think>\nOkay,... |
7.5. Vasya had 101 real coins. One of them was replaced with a fake one (it differs in weight, but it is unknown whether it is lighter or heavier than a real coin). Vasya wants to find as many real coins as possible in one weighing on a balance scale without weights. What should he do and how many real coins will he be... | <think>
Okay, let's see. Vasya has 101 coins, and one of them is fake. The fake one is either lighter or heavier, but we don't know which. He wants to find as many real coins as possible using just one weighing on a balance scale. Hmm, interesting problem. So, the key here is that he can only do one weighing, and from ... | [
{
"from": "human",
"value": "7.5. Vasya had 101 real coins. One of them was replaced with a fake one (it differs in weight, but it is unknown whether it is lighter or heavier than a real coin). Vasya wants to find as many real coins as possible in one weighing on a balance scale without weights. What should... |
976. Find the following limits:
1) $\lim _{\substack{x \rightarrow 2 \\ y \rightarrow 0}} \frac{\tan x y}{y}$
2) $\lim _{\substack{x \rightarrow 0 \\ y \rightarrow 0}} \frac{x+y}{x}$. | <think>
Okay, let's try to solve these two limit problems. Hmm, starting with the first one: the limit as x approaches 2 and y approaches 0 of tan(xy)/y. Hmm, okay. So we have variables x and y approaching different values here. X is going to 2, and y is going to 0. The expression is tan(xy) divided by y. I remember th... | [
{
"from": "human",
"value": "976. Find the following limits:\n1) $\\lim _{\\substack{x \\rightarrow 2 \\\\ y \\rightarrow 0}} \\frac{\\tan x y}{y}$\n2) $\\lim _{\\substack{x \\rightarrow 0 \\\\ y \\rightarrow 0}} \\frac{x+y}{x}$."
},
{
"from": "gpt",
"value": "<think>\nOkay, let's try to solve t... |
1. Find the minimum value of the expression $2 x+y$, defined on the set of all pairs $(x, y)$ satisfying the condition
$$
3|x-y|+|2 x-5|=x+1
$$ | <think>
Okay, let me try to figure out how to find the minimum value of 2x + y given the condition 3|x - y| + |2x - 5| = x + 1. Hmm, this looks like an absolute value equation constraint. I remember that absolute value equations can often be tackled by considering different cases based on the critical points where the ... | [
{
"from": "human",
"value": "1. Find the minimum value of the expression $2 x+y$, defined on the set of all pairs $(x, y)$ satisfying the condition\n\n$$\n3|x-y|+|2 x-5|=x+1\n$$"
},
{
"from": "gpt",
"value": "<think>\nOkay, let me try to figure out how to find the minimum value of 2x + y given t... |
4. If $-\frac{2}{3}<x<0, y=a x^{3}+a x^{2}+b \quad(a \neq 0)$ is a decreasing function, then the range of values for $\mathrm{a}$ is $\qquad$ . | <think>
Okay, let's see. I need to find the range of values for 'a' such that the function y = a x³ + a x² + b is decreasing when x is between -2/3 and 0. Hmm, right. Since the problem mentions the function being decreasing, I remember that for a function to be decreasing, its derivative should be negative in that inte... | [
{
"from": "human",
"value": "4. If $-\\frac{2}{3}<x<0, y=a x^{3}+a x^{2}+b \\quad(a \\neq 0)$ is a decreasing function, then the range of values for $\\mathrm{a}$ is $\\qquad$ ."
},
{
"from": "gpt",
"value": "<think>\nOkay, let's see. I need to find the range of values for 'a' such that the func... |
In a large hospital with several operating rooms, ten people are each waiting for a 45 minute operation. The first operation starts at 8:00 a.m., the second at 8:15 a.m., and each of the other operations starts at 15 minute intervals thereafter. When does the last operation end?
(A) 10:15 a.m.
(B) 10:30 a.m.
(C) 10:45 ... | <think>
Okay, let's see. The problem is about scheduling ten operations in a hospital. Each operation takes 45 minutes. The first one starts at 8:00 a.m., the second at 8:15 a.m., and each subsequent operation starts at 15-minute intervals. We need to figure out when the last operation ends. The answer choices are from... | [
{
"from": "human",
"value": "In a large hospital with several operating rooms, ten people are each waiting for a 45 minute operation. The first operation starts at 8:00 a.m., the second at 8:15 a.m., and each of the other operations starts at 15 minute intervals thereafter. When does the last operation end?... |
[ Touching circles ] [Common tangent to two circles]
Two touching circles are inscribed in an angle of size $2 \alpha$. Find the ratio of the radius of the smaller circle to the radius of a third circle that touches the first two circles and one of the sides of the angle. | <think>
Okay, so I have this problem here about two touching circles inscribed in an angle of size 2α. I need to find the ratio of the radius of the smaller circle to the radius of a third circle that touches the first two circles and one of the sides of the angle. Hmm, let me try to visualize this.
First, let me draw... | [
{
"from": "human",
"value": "[ Touching circles ] [Common tangent to two circles]\n\nTwo touching circles are inscribed in an angle of size $2 \\alpha$. Find the ratio of the radius of the smaller circle to the radius of a third circle that touches the first two circles and one of the sides of the angle."
... |
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