problem
stringlengths
14
4.09k
solution
stringlengths
1
802k
task_type
stringclasses
3 values
problem_tokens
int64
5
895
Given an ellipse in the Cartesian coordinate system $xOy$, its center is at the origin, the left focus is $F(-\sqrt{3},0)$, and the right vertex is $D(2,0)$. Let point $A(1, \frac{1}{2})$. $(1)$ Find the standard equation of the ellipse; $(2)$ Given that line $l$ intersects the ellipse and the midpoint of chord $BC$...
1 + \frac{\sqrt{3}}{2}
math
130
Simplify the expression $2 - \frac{2}{2 + \sqrt{5}} + \frac{2}{2 - \sqrt{5}}$. A) $2 - 4\sqrt{5}$ B) $2 + 4\sqrt{5}$ C) $2$ D) $-4\sqrt{5}$
2 - 4\sqrt{5}
math
75
Given $a \gt 0$, $b\in R$, if the inequality $\left(ax-2\right)(-x^{2}-bx+4)\leqslant 0$ holds for all $x \gt 0$, then the minimum value of $b+\frac{3}{a}$ is ______.
2\sqrt{2}
math
68
A graph has \( 12k \) vertices. Each vertex is connected by \( 3k+6 \) edges. For any two vertices, the number of vertices connected to both of them is the same. Determine the value of \( k \).
3
math
53
How many positive integers less than $100$ yield a remainder of $2$ when divided by $7$? What is the sum of these numbers?
665
math
33
Given a geometric sequence $\{a_n\}$ with a sum of the first $n$ terms as $S_n$, and $S_{10}:S_5 = 1:2$, find the value of $\frac{S_5 + S_{10} + S_{15}}{S_{10} - S_5}$.
-\frac{9}{2}
math
75
Given the function $f(x)=a\ln x- \frac {1}{2}x^{2}+x$, $g(x)= \frac {1}{2}x^{2}-2x+1$. (I) When $a=2$, find the maximum and minimum values of $f(x)$ for $x\in[1,e^{2}]$ (Reference data: $e^{2}\approx7.4$); (II) If for all $x\in(0,+\infty)$, $f(x)+g(x)\leqslant 0$ always holds, find the value of the real number $a$.
1
math
139
Given that the circumcenter O of triangle $ABC$ satisfies $\overrightarrow{AO} = \frac{1}{3}(\overrightarrow{AB} + \overrightarrow{AC})$, find the value of $\cos A$.
\frac{1}{2}
math
48
Five students (including A, B, C) are arranged in a row. A must be adjacent to B, and A must not be adjacent to C. The number of different ways to arrange them is _____. (Provide your answer in numerical form)
36
math
51
Team A and Team B play a series of games where the first team to win three games wins the series. Each team is equally likely to win each game, there are no ties, and the outcomes of the individual games are independent. Additionally, it's given that Team A never wins two consecutive games until they win the final game...
1
math
107
Given the price of an item increased by 30% in February, decreased by 10% in March, increased by 15% in April, and then decreased by $y\%$ in May, determine the percentage $y$ such that the price of the item at the end of May is the same as it had been at the beginning of February.
26
math
76
What is the greatest common divisor of 1729 and 1337?
7
math
19
Given an arithmetic sequence $\{a_n\}$ with the sum of the first $n$ terms denoted as $S_n$ and a common difference of $1$, if $S_6=3S_3$, then calculate the value of $a_9$.
a_9=a_1+8d=2+8=10
math
56
Given a circle $C: x^{2}+y^{2}=16$ and a line $l: (a-b)x + (3b-2a)y - a = 0$ where $a$ and $b$ are not both zero. As $a$ and $b$ vary, the minimum value of the chord length intercepted by the circle $C$ and the line $l$ is ____.
2\sqrt{6}
math
88
Calculate the slope angle of the line $x+2=0$.
\frac {π}{2}
math
14
Ms. Chen has two options to commute to her office via routes X and Y. Route X is 8 miles long and she travels at an average speed of 40 miles per hour. Route Y is a total of 7 miles, consisting of 5.5 miles traveled at 50 miles per hour, a 1-mile stretch at 10 miles per hour due to construction, and a 0.5-mile stretch ...
2.1
math
113
Given the function $f(x)=|x|+2^{|x|}$, and it satisfies $f(a-1) < f(2)$, the range of values for the real number $a$ is _____.
(-1,3)
math
47
How many lattice points lie on the graph of the equation $x^2 + y^2 = 72$?
12
math
25
Given \( f(u) = u^{2} + au + (b-2) \), where \( u = x + \frac{1}{x} \) (with \( x \in \mathbb{R} \) and \( x \neq 0 \)). If \( a \) and \( b \) are real numbers such that the equation \( f(u) = 0 \) has at least one real root, find the minimum value of \( a^{2} + b^{2} \).
4/5
math
109
Solve the following equation: $$ 2x^{4} + 2y^{4} - 4x^{3}y + 6x^{2}y^{2} - 4xy^{3} + 7y^{2} + 7z^{2} - 14yz - 70y + 70z + 175 = 0. $$
(x, y, z) = (0, 0, -5)
math
85
Given an ellipse C: $$\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$$ with $a > b > 0$, draw a perpendicular line from the right focus F<sub>2</sub> to the x-axis that intersects ellipse C at point P. If $\sin\angle PF_1F_2 = \frac{1}{3}$, determine the relationship between $a$ and $b$.
\sqrt{2}b
math
100
For every real number \( x \), evaluate the expression \( (x+1)^{2} - x^{2} \).
2x + 1
math
27
Given the parabola $y^{2}=8x$ whose directrix intersects with the hyperbola $\dfrac {x^{2}}{a^{2}}- \dfrac {y^{2}}{b^{2}}=1$ ($a > 0,b > 0$) at points $A$ and $B$, and one of the asymptotes of the hyperbola is $y= \dfrac {4 \sqrt {3}}{3}x$, find the standard equation of the hyperbola.
\dfrac {x^{2}}{3}- \dfrac {y^{2}}{16}=1
math
112
Let \( A \) be the set of any 20 points on the circumference of a circle. Joining any two points in \( A \) produces one chord of this circle. Suppose every three such chords are not concurrent. Find the number of regions within the circle which are divided by all these chords.
5036
math
63
How many increasing arithmetic progressions are there consisting of 22 different natural numbers, where all numbers are not greater than 1000?
23312
math
30
For which integer $c$ does $x^2 + x + c$ divide $x^{13} - x + 106$?
2
math
32
The point that is $4$ units away from the origin on the number line represents the number $x$ such that $|x|=4$.
4 \text{ or } -4
math
30
Consider an equilateral triangle $ABC$ with side length $3$. Right triangle $CBD$ is constructed outwardly on side $BC$ of triangle $ABC$ such that $CB = BD$ and $BCD$ is a right angle at $B$. Find $\sin^2\left(\angle CAD\right)$. A) $\frac{3}{4}$ B) $\frac{1}{4}$ C) $\frac{1}{2}$ D) $\frac{\sqrt{2}}{2}$ E) $\f...
\frac{1}{2}
math
122
The product of the digits of 1423 is 24. Find how many distinct four-digit positive integers have a product of their digits equal to 18.
36
math
36
Find all positive integers \( m \), \( n \) such that \( \frac{1}{m} + \frac{1}{n} - \frac{1}{mn} = \frac{2}{5} \).
(3, 10), (10, 3), (4, 5), (5, 4)
math
48
Given the function $f\left( x \right)=a{{x}^{2}}+x-\ln x$, determine the range of values for the real number $a$ such that the function is monotonically increasing on $\left( 2,+\infty \right)$.
\left[ 0, +\infty \right)
math
60
In the quadratic equation $x^{2}-2ax+b=0$, if $a^{2}-b \gt 0$, then $a$ is called the midpoint value of the equation.<br/>$(1)$ The midpoint value of the equation $x^{2}-8x+3=0$ is ______.<br/>$(2)$ Given that the midpoint value of the equation $x^{2}-mx+n=0$ is $3$, and one of the roots is exactly equal to $n$, find t...
n = 5
math
112
Given the ellipse $C: \frac{x^{2}}{2}+y^{2}=1$ and the line $l: y=x+\sqrt{3}$, calculate the maximum distance from a point on the ellipse C to the line l.
\sqrt{6}
math
52
In $\triangle ABC$, the sides opposite to angles $A$, $B$, and $C$ are denoted as $a$, $b$, and $c$ respectively, and it is given that $2b\cdot\cos A=c\cdot\cos A+a\cdot\cos C$. $(1)$ Find the magnitude of angle $A$; $(2)$ If $a=\sqrt{7}$ and $b+c=4$, find the value of $bc$.
3
math
101
Elective 4-4: Coordinate System and Parametric Equations In the Cartesian coordinate system $xOy$, the curve $C$ is given by the parametric equations: \[ \begin{cases} x=1+ \sqrt{3}\cos \varphi \\ y= \sqrt{3}\sin \varphi \end{cases} \] where $\varphi$ is the parameter, $0 \leqslant \varphi \leqslant \pi$. A polar coo...
5
math
249
Given that the points $(1, -2)$, $(3, 4)$, and $(6, m/3)$ are on the same straight line, find the value(s) of $m$. **A)** $27$ **B)** $39$ **C)** $52$ **D)** $15$
39
math
71
Given that $P$ is a point on the parabola $y^2=4x$, let the distance from $P$ to the directrix be $d_1$, and the distance from $P$ to point $A(1, 4)$ be $d_2$. Find the minimum value of $d_1+d_2$.
4
math
74
Mr. $X$ owns a home worth $$20,000$. He sells it to Mr. $Y$ at a $15\%$ profit. Mr. $Y$ then sells the house back to Mr. $X$ at a $15\%$ loss. How much did Mr. $X$ gain or lose in the end? A) Mr. X gains $3500$ B) Mr. X gains $3450$ C) Mr. X loses $3450$ D) Mr. X gains $3200$
3450
math
125
Given point $A(1,2)$ and circle $C: x^{2}+y^{2}+2mx+2y+2=0$. $(1)$ If there are two tangents passing through point $A$, find the range of $m$. $(2)$ When $m=-2$, a point $P$ on the line $2x-y+3=0$ is chosen to form two tangents $PM$ and $PN$ to the circle. Find the minimum area of quadrilateral $PMCN$.
\frac{7\sqrt{15}}{5}
math
113
Given that $y$ is a quadratic function of $x$ in the form of $y=ax^{2}-bx+2 (a\ne 0).$ (1) When $a=-2$, $b=-4$, find the axis of symmetry and the vertex coordinates of the function graph. (2) Under the conditions in (1), $Q(m,t)$ is a point on the graph, and its symmetric point $P$ about the origin also falls on the ...
y_{1} > y_{2}
math
186
From a group of 4 male students and 6 female students, determine the number of different ways to select 3 people to participate in a club activity, such that both male and female students are included.
96
math
42
Fill in the blanks with appropriate numbers. 4 liters 25 milliliters = ___ milliliters 6.09 cubic decimeters = ___ cubic centimeters 4.9 cubic decimeters = ___ liters ___ milliliters 2.03 cubic meters = ___ cubic meters ___ cubic decimeters.
30
math
65
Sally has 12 blue marbles and 8 red marbles in a bag. She removes a marble at random, records the color, puts it back, and then repeats this process until she has withdrawn 8 marbles. What is the probability that exactly five of the marbles that she removes are blue? Express your answer as a decimal rounded to the near...
0.279
math
78
What is the value of the following expression: $2 - 5 + 8 - 11 + 14 - \cdots - 47 + 50 - 53 + 56$ ?
29
math
47
For a natural number $A$, define the product of its digits in base 10 as $p(A)$. Find all values of $A$ that satisfy the equation $A = 1.5 \cdot p(A)$.
48
math
48
Express 1.59 million in scientific notation.
1.59 \times 10^{6}
math
11
Sides $\overline{AJ}$ and $\overline{EF}$ of regular decagon $ABCDEFGHIJ$ are extended to meet at point $Q$. What is the degree measure of angle $Q$?
72^\circ
math
43
The diagonal of a particular square is 6 inches. The diameter of a particular circle is 8 inches. By how many square inches is the area of the circle greater than the area of the square? Express your answer as a decimal to the nearest tenth.
32.3
math
52
The square of an integer is 140 greater than three times the integer itself. What is the sum of all integers for which this is true?
4
math
31
For the given ellipse, calculate the distance between the foci. The ellipse is centered at point (2,2) with a semi-major axis of 5 units and a semi-minor axis of 3 units.
8
math
44
Given $|a| = 4$, $|b| = 5$, and $|a + b| = -(a + b)$, find the value of $2a - b$.
2a - b = 13 \text{ or } -3
math
41
There are 100 silver coins, ordered by weight, and 101 gold coins, also ordered by weight. It is known that all coins have different weights. We have a two-pan balance scale that allows us to determine which of any two coins is heavier. How can we find the coin that ranks 101st in weight among all the coins with the mi...
8 \text{ weighings}
math
84
The constant term in the expansion of ${(1+x+\frac{1}{{x}^{2}})}^{5}$ can be found by calculating the coefficient of the term with no $x$ in it.
31
math
43
Let $a$ and $b$ be positive integers such that $a-b=8$ and $\text{gcd}\left(\frac{a^3+b^3}{a+b}, ab\right) = 16$. Find the smallest possible value of $b$.
4
math
57
Calculate the indefinite integral: $$ \int \frac{x \cdot \cos x + \sin x}{(x \cdot \sin x)^{2}} \, dx $$
-\frac{1}{x \sin x} + C
math
38
Given that each player requires one pair of shoes and one uniform for local matches, and the same pair for international games, where shoes cost $10 per pair and each uniform costs $15 more than a pair of shoes, and the total expenditure for the gear is $5600, calculate the number of players in the Club.
80
math
69
For a finite sequence \(P = \left(p_1, p_2, \cdots, p_n\right)\), the Cesaro sum (named after the mathematician Cesaro) is defined as \(\frac{1}{n}(S_1 + S_2 + \cdots + S_n)\), where \(S_k = p_1 + p_2 + \cdots + p_k\) for \(1 \leq k \leq n\). If a sequence \(\left(p_1, p_2, \cdots, p_{99}\right)\) of 99 terms has a Ces...
991
math
182
For a positive integer \( n \), let \( x_n \) be the real root of the equation \( n x^{3} + 2 x - n = 0 \). Define \( a_n = \left[ (n+1) x_n \right] \) (where \( [x] \) denotes the greatest integer less than or equal to \( x \)) for \( n = 2, 3, \ldots \). Then find \( \frac{1}{1005} \left( a_2 + a_3 + a_4 + \cdots + a...
2013
math
138
Given that segment AB passes through the center of the ellipse $\frac{x^2}{8} + \frac{y^2}{4} = 1$ with points A and B on the ellipse, and $F_1$, $F_2$ being the two foci of the ellipse, find the maximum area of the quadrilateral $F_1AF_2B$.
8
math
79
Given positive numbers $a$ and $b$ that satisfy the equation $3ab - 3 = a + 3b$, find the minimum value of $a + 3b$.
6
math
39
A tourist travels from point \(A\) to point \(B\) in 1 hour and 56 minutes. The route from \(A\) to \(B\) first goes uphill, then on flat terrain, and finally downhill. What is the length of the flat terrain if the tourist's speed downhill is 6 km/h, uphill is 4 km/h, and on flat terrain is 5 km/h, and the total distan...
3
math
115
The length of the chord cut by the line $y=2x-2$ on the circle $(x-2)^{2}+(y-2)^{2}=25$ can be calculated.
10
math
43
Given a set of sample data with $9$ numbers, the average is $8$, and the variance is $12$. After adding one more data point to this set, the new average of the sample data becomes $9$. Calculate the variance of the new sample data.
19.8
math
56
From the numbers 1 to 200, one or more numbers were selected to form a group with the following property: if the group contains at least two numbers, then the sum of any two numbers in this group is divisible by 5. What is the maximum number of numbers that can be in the group with this property?
40
math
68
How many ordered pairs of real numbers $(x, y)$ satisfy the following system of equations? \[ \left\{ \begin{aligned} x + 2y &= 2 \\ \left| |x| - 2|y| \right| &= 2 \end{aligned} \right. \]
2
math
73
Given a function $f(x)$ defined on $\mathbb{R}$ that satisfies the equation $f(x)+f(1-x)=1$ for all $x$, and for $x \geqslant 0$ the relation $f\left(\dfrac{x}{3}\right)=\dfrac{1}{2}f(x)$ holds, and for $0 \leqslant x_1 < x_2 \leqslant 1$, $f(x_1)\leqslant f(x_2)$, find the value of $f\left(\dfrac{1}{2018}\right)$.
\dfrac{1}{128}
math
137
A cylinder has a radius of 5 cm and a height of 12 cm. What is the longest segment that would fit inside this cylinder?
2\sqrt{61} \text{ cm}
math
30
The height of the pillar at D is 17 meters, but reformatted question is: What is the height of the pillar at D?
17
math
29
What is the sum of $\left(\dfrac{1}{4}\right) + \left(\dfrac{1}{4}\right)^2 + \left(\dfrac{1}{4}\right)^3 + \left(\dfrac{1}{4}\right)^4 + \left(\dfrac{1}{4}\right)^5 + \left(\dfrac{1}{4}\right)^6$?
\frac{4095}{12288}
math
89
A factory produces a certain product, and the defective rate $p$ is related to the daily output $x$ (in ten thousand units) as follows: $P= \begin{cases} \dfrac {1}{6-x}, & 0 < x\leqslant c \\ \dfrac {2}{3}, & x > c\end{cases}$ ($c$ is a constant, and $0 < c < 6$). It is known that for every qualified product produced,...
3
math
215
Suppose $X$ is a random variable that takes on only nonnegative integer values, with $E\left[ X \right] = 1$, $E\left[ X^2 \right] = 2$, and $E \left[ X^3 \right] = 5$. Determine the smallest possible value of the probability of the event $X=0$.
\frac{1}{3}
math
79
In \\(\Delta ABC\\), with \\(A=60^\circ\\), \\(b=1\\), and the area being \\(\sqrt{3}\\), find the value of \\(\dfrac{a+b+c}{\sin A+\sin B+\sin C}\\).
\dfrac{2\sqrt{39}}{3}
math
60
The graph of the parabola defined by the equation \( y = (x-2)^2 + 3 \) is rotated 180 degrees about its vertex, then shifted 4 units to the left, and then shifted 3 units down. Find the sum of the zeros of the resulting parabola.
-4
math
66
Consider the line integral $$ \int_{L} \frac{-y \, dx}{x^{2}+y^{2}}+\frac{x \, dy}{x^{2}+y^{2}} $$
2\pi
math
46
Angle $EAB$ is a right angle, and $BE = 12$ units. Additionally, a point $H$ is placed such that triangle $EAH$ is also a right triangle with $AH = 5$ units. Determine the number of square units in the sum of the areas of the three squares $ABCD$, $AEFG$, and $AHIJ$.
169
math
80
A frequency distribution of the scores for Mr. Sampson's algebra class is shown. What percent of the class received a score in the $60\%$-$69\%$ range? \begin{tabular}{|c|c|} Test Scores & Frequencies\\ \hline $90\% - 100\%$& IIII\\ $80\% - 89\%$& IIII IIII\\ $70\% - 79\%$& IIII II\\ $60\% - 69\%$ & IIII I\\ Below $60\...
20\%
math
152
Let $h_1$ and $h_2$ be the altitudes of a triangle drawn to the sides with length 5 and $2\sqrt 6$, respectively. If $5 + h_1 \leq 2\sqrt 6 + h_2$, determine the length of the third side of the triangle.
7
math
69
Given that $3^a = 4^b = 5^c = 6$, find the value of $\frac {1}{a}+ \frac {1}{b}+ \frac {1}{c}$.
\log_{6} 60
math
48
Factor the following expression: $74a^2 + 222a + 148a^3$.
74a(2a^2 + a + 3)
math
26
Given the function $f(x)=x^{3}- \frac {3}{2}x^{2}+ \frac {3}{4}x+ \frac {1}{8}$, find the value of $\sum\limits_{k=1}^{2016}f( \frac {k}{2017})$.
504
math
72
Given the expansion of \\((x^3+ \frac{1}{ \sqrt{x}})^n \\) contains a constant term and the minimum value of \\(n\\) is \\(a\\), evaluate \\(\int\_{-a}^{a} \sqrt{{a}^{2}-{x}^{2}}dx \\).
\frac{49π}{2}
math
71
Given the functions $f(x)=2(x+1)$ and $g(x)=x+ \ln x$, points $A$ and $B$ are located on the graphs of $f(x)$ and $g(x)$ respectively, and their y-coordinates are always equal. Calculate the minimum distance between points $A$ and $B$.
\frac{3}{2}
math
70
Given an isosceles triangle \(XYZ\) with \(XY = YZ\) and an angle at the vertex equal to \(96^{\circ}\). Point \(O\) is located inside triangle \(XYZ\) such that \(\angle OZX = 30^{\circ}\) and \(\angle OXZ = 18^{\circ}\). Find the measure of angle \(\angle YOX\).
78
math
88
Find all integers \( n \) such that \( n^5 + 3 \) is divisible by \( n^2 + 1 \).
-3, -1, 0, 1, 2
math
30
In the diagram, \( PQR \) is a line segment, \( \angle PQS = 125^\circ \), \( \angle QSR = x^\circ \), and \( SQ = SR \). What is the value of \( x \)?
70
math
55
Expand the binomial ${(\sqrt{x}-\frac{2}{x})^{n}}$: (1) If $n=6$, find the second to last term. (2) If the coefficient ratio of the 5th term to the 3rd term is $56:3$, find the sum of all binomial coefficients.
1024
math
72
The quadratic function \( f(x) = ax^2 + bx + c \) (where \( a, b, c \in \mathbb{R} \) and \( a \neq 0 \)) satisfies the following conditions: 1. \( f(-1) = 0 \); 2. For all \( x \in \mathbb{R} \), \( f(x) \geq x \); 3. For all \( x \in (0, 2) \), \( f(x) \leq \frac{(x + 1)^2}{4} \). Given \( x_1, x_2, x_3 \in (0, 2) \...
1
math
207
The entry fee for a concert is \$30 per adult and \$15 per child. On a particular day, the concert collected \$2250 in entry fees, with at least one adult and one child attending. Determine the ratio of adults to children on that day, such that the ratio is closest to 1.
1
math
67
Given that the three vertices of $\triangle ABC$ are $A(4,0)$, $B(6,7)$, and $C(0,3)$. $(1)$ Find the equation of the line containing the altitude of side $BC$. $(2)$ Find the equation of the line that bisects the area of $\triangle ABC$ and passes through point $B$.
11x - 8y - 10 = 0
math
82
A certain school's second-year junior high students from classes A and B participated in the Hua Cup competition, totaling $a$ students. The average score of class A was 71 points per student, and the average score of class B was 69 points per student. The total score of the two classes was 3480 points. How many studen...
50
math
85
Suppose $g(x)$ is a function defined for all real $x$, and suppose $g$ is invertible. Consider the graphs of $y=g(x^3)$ and $y=g(x^6)$. How many points do they intersect?
2
math
52
Given that $f(x)$ is an odd function defined on $\mathbb{R}$, for $x \in [0, +\infty)$, $f(x) = 2^x + x - m$ (where $m$ is a constant). (1) Determine the value of the constant $m$. (2) Determine the explicit formula for $f(x)$. (3) If it holds true that for any $x \in [-3, -2]$, $f(k \cdot 4^x) + f(1 - 2^{x+1}) > 0$, f...
k \in (-8, +\infty)
math
139
Given that the sum of the first n terms of a geometric sequence {a_{n}} is S_{n}, if S_{3} = 7 and S_{6} = 63, find the value of a_{1}.
1
math
49
If one focus of the hyperbola $\left({{x}^{2}}-\dfrac{{{y}^{2}}}{m}=1\right)$ is at $(-3,0)$, determine the value of $m$.
8
math
49
The equation of the line through $(4,3)$ and $(12,-3)$ is $\frac{x}{a}+\frac{y}{b}=1$. Find $a$.
8
math
38
A starship enters an extraordinary meteor shower. Some of the meteors travel along a straight line at the same speed, equally spaced. Another group of meteors travels similarly along another straight line, parallel to the first, with the same speed but in the opposite direction, also equally spaced. The ship travels p...
9.1
math
171
What is the positive difference between the $2000^{\mathrm{th}}$ term and the $2005^{\mathrm{th}}$ term of the arithmetic sequence $-8,$ $-2,$ $4,$ $10,$ $\ldots$?
30
math
59
\( A_1, A_2, A_3, A_4 \) are consecutive vertices of a regular \( n \)-gon. Given the equation \( \frac{1}{A_1A_2} = \frac{1}{A_1A_3} + \frac{1}{A_1A_4} \), what are the possible values of \( n \)?
n = 7
math
84
Choose three people from five, including A and B, to form a line. What is the probability that person A is not in the first position and person B is not in the last position?
\frac {13}{20}
math
39
Given the sequence {a<sub>n</sub>} with the sum of its first n terms S<sub>n</sub> = n<sup>2</sup> - 2n + 2, find a<sub>1</sub> and a<sub>n</sub>.
1
math
60