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<p> Let a differentiable function $$f$$ satisfy $$f(x)+\int_\limits{3}^{x} \frac{f(t)}{t} d t=\sqrt{x+1}, x \geq 3$$. Then $$12 f(8)$$ is equal to :</p>
Options:
[{"identifier": "A", "content": "19"}, {"identifier": "B", "content": "34"}, {"identifier": "C", "content": "17"}, {"identifier": "D", "content": "1"}] | ["C"]
Explanation:
Differentiating both sides we get,
<br/><br/>$$
\begin{aligned}
& f^{\prime}(x)+\frac{f(x)}{x}=\frac{1}{2 \sqrt{x+1}} \\\\
& \Rightarrow \frac{d y}{d x}+\frac{y}{x}=\frac{1}{2 \sqrt{x+1}} \\\\
& \Rightarrow \mathrm{IF}=x \\\\
& \Rightarrow y x=\frac{1}{2} \int \frac{x}{\sqrt{x+1}} d x+c \\\\
& \Rig... |
<p>Let $$f(x)$$ be a positive function such that the area bounded by $$y=f(x), y=0$$ from $$x=0$$ to $$x=a>0$$ is $$e^{-a}+4 a^2+a-1$$. Then the differential equation, whose general solution is $$y=c_1 f(x)+c_2$$, where $$c_1$$ and $$c_2$$ are arbitrary constants, is</p>
Options:
[{"identifier": "A", "content": "$$... | ["B"]
Explanation:
<p>$$\int_\limits0^a f(x) d x=e^{-a}+4 a^2+a-1$$</p>
<p>Differentiate equation w.r.t. 'a'</p>
<p>$$\begin{aligned}
& f(a)=-e^{-a}+8 a+1 \\
& \Rightarrow f(x)=-e^{-x}+8 x+1
\end{aligned}$$</p>
<p>And $$y=c_1 f(x)+c_2$$</p>
<p>$$\begin{aligned}
& y=c_1\left(-e^{-x}+8 x+1\right)+c_2 \\
& y^{\prime}=c_1... |
<p>The differential equation of the family of circles passing through the origin and having centre at the line $$y=x$$ is :</p>
Options:
[{"identifier": "A", "content": "$$\\left(x^2-y^2+2 x y\\right) \\mathrm{d} x=\\left(x^2-y^2+2 x y\\right) \\mathrm{d} y$$\n"}, {"identifier": "B", "content": "$$\\left(x^2+y^2-2 x y... | ["D"]
Explanation:
<p>Equation of circle passing through origin & having centre at the line $$y=x$$ is</p>
<p><img src="https://app-content.cdn.examgoal.net/fly/@width/image/1lwegsauf/ce0513c1-e394-4ced-87e0-f3bb34e8f595/28467680-1661-11ef-a209-0180f41f1307/file-1lwegsaug.png?format=png" data-orsrc="https://app-co... |
The solution of the differential equation
<br/><br/>$$\left( {1 + {y^2}} \right) + \left( {x - {e^{{{\tan }^{ - 1}}y}}} \right){{dy} \over {dx}} = 0,$$ is :
Options:
[{"identifier": "A", "content": "$$x{e^{2{{\\tan }^{ - 1}}y}} = {e^{{{\\tan }^{ - 1}}y}} + k$$ "}, {"identifier": "B", "content": "$$\\left( {x - 2} \\r... | ["C"]
Explanation:
$$\left( {1 + {y^2}} \right) + \left( {x - {e^{{{\tan }^{ - 1}}y}}} \right){{dy} \over {dx}} = 0$$
<br><br>$$ \Rightarrow {{dx} \over {dy}} + {x \over {\left( {1 + {y^2}} \right)}} = {{{e^{{{\tan }^{ - 1}}y}}} \over {\left( {1 + {y^2}} \right)}}$$
<br><br>$$I.F = e{}^{\int {{1 \over {\left( {1 + {y^... |
The solution of the differential equation
<br/><br>$${{dy} \over {dx}} = {{x + y} \over x}$$ satisfying the condition $$y(1)=1$$ is :</br>
Options:
[{"identifier": "A", "content": "$$y = \\ln x + x$$ "}, {"identifier": "B", "content": "$$y = x\\ln x + {x^2}$$ "}, {"identifier": "C", "content": "$$y = x{e^{\\left( {x ... | ["D"]
Explanation:
$${{dy} \over {dx}} = {{x + y} \over x} = 1 + {y \over x}$$
<br><br>Putting $$y=$$ $$vx$$
<br><br>and $${{dy} \over {dx}} = v + x{{dv} \over {dx}}$$
<br><br>we get
<br><br>$$v + x{{dv} \over {dx}} = 1 + v$$
<br><br>$$ \Rightarrow \int {{{dx} \over x}} = \int {dv} $$
<br><br>$$ \Rightarrow v = \ln ... |
If $${{dy} \over {dx}} = y + 3 > 0\,\,$$ and $$y(0)=2,$$ then $$y\left( {\ln 2} \right)$$ is equal to :
Options:
[{"identifier": "A", "content": "$$5$$"}, {"identifier": "B", "content": "$$13$$"}, {"identifier": "C", "content": "$$-2$$"}, {"identifier": "D", "content": "$$7$$"}] | ["D"]
Explanation:
$${{dy} \over {dx}} = y + 3 \Rightarrow \int {{{dy} \over {y + 3}}} = \int {dx} $$
<br><br>$$ \Rightarrow \ell n\left| {y + 3} \right| = x + c$$
<br><br>Since $$y\left( 0 \right) = 2,\,\,\,$$ $$\,\,\,\,\,\,\,$$ $$\therefore$$ $$\,\,\,\,\,\,\,$$ $$\ell n5 = c$$
<br><br>$$ \Rightarrow \ell n\left| {y... |
Let $$y(x)$$ be the solution of the differential equation
<br/><br>$$\left( {x\,\log x} \right){{dy} \over {dx}} + y = 2x\,\log x,\left( {x \ge 1} \right).$$ Then $$y(e)$$ is equal to :</br>
Options:
[{"identifier": "A", "content": "$$2$$ "}, {"identifier": "B", "content": "$$2e$$ "}, {"identifier": "C", "content": "... | ["A"]
Explanation:
Given, $${{dy} \over {dx}} + \left( {{1 \over {x\,\log \,x}}} \right)y = 2$$
<br><br>$$I.F. = {e^{\int {{1 \over {x\log x}}dx} }} = {e^{\log \left( {\log x} \right)}} = \log x$$
<br><br>$$y.\log x = \int {2\,\log xdx + c} $$
<br><br>$$y\log x = 2\left[ {x\log x - x} \right] + c$$
<br><br>Put $$x=1,y... |
The solution of the differential equation
<br/><br/>$${{dy} \over {dx}}\, + \,{y \over 2}\,\sec x = {{\tan x} \over {2y}},\,\,$$
<br/><br/>where 0 $$ \le $$ x < $${\pi \over 2}$$, and y (0) = 1, is given by :
Options:
[{"identifier": "A", "content": "y = 1 $$-$$ $${x \\over {\\sec x + \\tan x}}$$ "}, {"identif... | ["C"]
Explanation:
Given,
<br><br>$${{dy} \over {dx}} + {y \over 2}\sec x = {{\tan x} \over {2y}}$$
<br><br>$$ \Rightarrow $$ $$2y{{dy} \over {dx}} + {y^2}\sec x = \tan x$$
<br><br>Now, let
<br><br>y<sup>2</sup> $$=$$ t
<br><br>$$ \Rightarrow $$ 2y$${{dy} \over {dx}} = {{dt} \over {d... |
If $$\left( {2 + \sin x} \right){{dy} \over {dx}} + \left( {y + 1} \right)\cos x = 0$$ and y(0) = 1,
<br/><br/>then $$y\left( {{\pi \over 2}} \right)$$ is equal to :
Options:
[{"identifier": "A", "content": "$$ - {2 \\over 3}$$"}, {"identifier": "B", "content": "$$ - {1 \\over 3}$$"}, {"identifier": "C", "content": "... | ["D"]
Explanation:
$$\left( {2 + \sin x} \right){{dy} \over {dx}} + \left( {y + 1} \right)\cos x = 0$$
<br><br>$$ \Rightarrow $$ $${d \over {dx}}\left( {2 + \sin x} \right)\left( {y + 1} \right) = 0$$
<br><br>On integrating, we get
<br><br>(2 + sin x) (y + 1) = C
<br><br>At x = 0, y = 1 we have
<br><br>(2 + sin 0) (1 ... |
The curve satisfying the differential equation, ydx $$-$$(x + 3y<sup>2</sup>)dy = 0 and passing through the point (1, 1), also passes through the point :
Options:
[{"identifier": "A", "content": "$$\\left( {{1 \\over 4}, - {1 \\over 2}} \\right)$$"}, {"identifier": "B", "content": "$$\\left( { - {1 \\over 3},{1 \\ov... | ["B"]
Explanation:
Given,
<br><br>y dx = $$\left( {x + 3{y^2}} \right)dy$$
<br><br>$$ \Rightarrow $$$$\,\,\,$$ y $${{dx} \over {dy}}$$ = x + 3y<sup>2</sup>
<br><br>$$ \Rightarrow $$$$\,\,\,$$ $${{dx} \over {dy}}$$ $$-$$ $${x \over y} = 3y$$
<br><br>If = $${e^{ - \int {{1 \over y}dy} }}$$... |
If 2x = y$${^{{1 \over 5}}}$$ + y$${^{ - {1 \over 5}}}$$ and
<br/><br/>(x<sup>2</sup> $$-$$ 1) $${{{d^2}y} \over {d{x^2}}}$$ + $$\lambda $$x $${{dy} \over {dx}}$$ + ky = 0,
<br/><br/>then $$\lambda $$ + k is equal to :
Options:
[{"identifier": "A", "content": "$$-$$ 23 "}, {"identifier": "B", "content": "$$-$$ 24 "... | ["B"]
Explanation:
<p>It is given that</p>
<p>$$2x = {y^{1/5}} + {y^{ - 1/5}}$$</p>
<p>$$ \Rightarrow 2x = {y^{1/5}} + 1/{y^{1/5}}$$</p>
<p>Therefore, $$2x = a + {1 \over a} \Rightarrow {a^2} - 2ax + 1 = 0$$</p>
<p>$$a = {{2x \pm \sqrt {4{x^2} - 4} } \over 2}$$</p>
<p>$$ \Rightarrow a = {{2x \pm 2\sqrt {{x^2} - 1} } \... |
Let y = y(x) be the solution of the differential equation
<br/><br/>$$\sin x{{dy} \over {dx}} + y\cos x = 4x$$, $$x \in \left( {0,\pi } \right)$$.
<br/><br/>If $$y\left( {{\pi \over 2}} \right) = 0$$, then $$y\left( {{\pi \over 6}} \right)$$ is equal to :
Options:
[{"identifier": "A", "content": "$$ - {4 \\over 9}{\... | ["D"]
Explanation:
Given,
<br><br> sin x $${{dy} \over {dx}} + y\cos y = 4x$$
<br><br>$$ \Rightarrow \,\,\,\,{{dy} \over {dx}}\,$$ + y cot x = 4x cosec x
<br><br>This is a linear differential equation of form,
<br><br> $${{dy} \over {dx}}\,$$ + py = Q
<br><br>Where p = cot x and Q = 4x cosec x
<br><br>So, Integrati... |
If y = y(x) is the solution of the differential equation,
<br/><br/>x$$dy \over dx$$ + 2y = x<sup>2</sup>, satisfying y(1) = 1, then y($$1\over2$$) is equal
to :
Options:
[{"identifier": "A", "content": "$$ {{7} \\over {64}}$$"}, {"identifier": "B", "content": "$$ {{49} \\over {16}}$$"}, {"identifier": "C", "content... | ["B"]
Explanation:
Given,
<br><br>$$x{{dy} \over {dx}} + 2y = {x^2}$$
<br><br>$$ \Rightarrow $$ $${{dy} \over {dx}} + \left( {{2 \over x}} \right)y = x$$
<br><br>This is a linear differential equation.
<br><br>$$ \therefore $$ I.F $$ = {e^{\int {{2 \over x}dx} }}$$
<br><br>$$ = {e^{2\ln x}}$$
<b... |
Let f be a differentiable function such that f '(x) = 7 - $${3 \over 4}{{f\left( x \right)} \over x},$$ (x > 0) and f(1) $$ \ne $$ 4. Then $$\mathop {\lim }\limits_{x \to 0'} \,$$ xf$$\left( {{1 \over x}} \right)$$ :
Options:
[{"identifier": "A", "content": "does not exist "}, {"identifier": "B", "content": "exists... | ["C"]
Explanation:
$$f'(x) = 7 - {3 \over 4}{{f\left( x \right)} \over x}\,\,\,\left( {x > 0} \right)$$
<br><br>Given f(1) $$ \ne $$ 4 $$\mathop {\lim }\limits_{x \to {0^ + }} \,xf\left( {{1 \over x}} \right)\, = ?$$
<br><br>$${{dy} \over {dx}} + {3 \over 4}{y \over x} = 7$$ (This ... |
The solution of the differential equation,
<br/><br/>$${{dy} \over {dx}}$$ = (x – y)<sup>2</sup>, when y(1) = 1, is :
Options:
[{"identifier": "A", "content": "$$-$$ log<sub>e</sub> $$\\left| {{{1 + x - y} \\over {1 - x + y}}} \\right|$$ = x + y $$-$$ 2"}, {"identifier": "B", "content": "log<sub>e</sub> $$\\left| {{... | ["D"]
Explanation:
x $$-$$ y = t <br><br>$$ \Rightarrow $$ $${{dy} \over {dx}} = 1 - {{dt} \over {dx}}$$
<br><br>$$ \Rightarrow $$ 1 $$-$$ $${{dt} \over {dx}}$$ = t<sup>2</sup> $$ \Rightarrow $$ $$\int {{{dt} \over {1 - {t^2}}}} $$ = $$\int {1dx} $$
<br><br>$$ \Rightarrow $$ $${1 ... |
Let y = y(x) be the solution of the differential equation, x$${{dy} \over {dx}}$$ + y = x log<sub>e</sub> x, (x > 1). If 2y(2) = log<sub>e</sub> 4 $$-$$ 1, then y(e) is equal to :
Options:
[{"identifier": "A", "content": "$$ - {e \\over 2}$$"}, {"identifier": "B", "content": "$$ - {{{e^2}} \\over 2}$$"}, {"ident... | ["D"]
Explanation:
$${{dy} \over {dx}} = {y \over x} = \ell nx$$
<br><br>$${e^{\int {{1 \over x}dx} }} = x$$
<br><br>$$xy = \int {x\ell nx + C} $$
<br><br>$$\ell nx{{{x^2}} \over 2} - \int {{1 \over x}.{{{x^2}} \over 2}} $$
<br><br>$$xy = {x \over 2}\ell nx - {{{x^2}} \over 4} + C,$$
<br><br>for $$2y\... |
If a curve passes through the point (1, –2) and has slope of the tangent at any point (x, y) on it as $${{{x^2} - 2y} \over x}$$, then the curve also passes through the point :
Options:
[{"identifier": "A", "content": "(\u20131, 2)"}, {"identifier": "B", "content": "$$\\left( { - \\sqrt 2 ,1} \\right)$$"}, {"identifie... | ["C"]
Explanation:
$${{dy} \over {dx}} = {{{x^2} - 2y} \over x}$$ (Given)
<br><br>$${{dy} \over {dx}} + 2{y \over x} = x$$
<br><br>I.F = $${e^{\int {{2 \over x}dx} }} = {x^2}$$
<br><br>$$ \therefore $$ y.... |
The solution of the differential equation
<br/><br/>$$x{{dy} \over {dx}} + 2y$$ = x<sup>2</sup> (x $$ \ne $$ 0) with y(1) = 1, is :
Options:
[{"identifier": "A", "content": "$$y = {4 \\over 5}{x^3} + {1 \\over {5{x^2}}}$$"}, {"identifier": "B", "content": "$$y = {3 \\over 4}{x^2} + {1 \\over {4{x^2}}}$$"}, {"identifie... | ["C"]
Explanation:
$$x{{dy} \over {dx}} + 2y$$ = x<sup>2</sup>
<br><br>$$ \Rightarrow $$ $${{dy} \over {dx}} + \left( {{2 \over x}} \right)y = x$$
<br><br>$$ \therefore $$ I.F = $${e^{\int {{2 \over x}dx} }}$$ = x<sup>2</sup>
<br><br>$$ \therefore $$ The solution is
<br><br>yx<sup>2</sup> = $$\int {{x^3}dx} $$
<br><br... |
If $$\cos x{{dy} \over {dx}} - y\sin x = 6x$$, (0 < x < $${\pi \over 2}$$)<br/>
and $$y\left( {{\pi \over 3}} \right)$$ = 0 then $$y\left( {{\pi \over 6}} \right)$$ is equal to :-
Options:
[{"identifier": "A", "content": "$$ - {{{\\pi ^2}} \\over {2 }}$$"}, {"identifier": "B", "content": "$$ - {{{\\pi ^2}} \\... | ["D"]
Explanation:
$$\cos x{{dy} \over {dx}} - y\sin x = 6x$$
<br><br>$$ \Rightarrow $$ $${{dy} \over {dx}} - y\tan x = 6x.\sec x$$
<br><br>This is a linear differential equation.
<br><br>$$ \therefore $$ I.F = $${e^{\int { - \tan xdx} }}$$ = $$\left| {\cos x} \right|$$
<br><br>As 0 < x < $${\pi \over 2}$$, so ... |
If y = y(x) is the solution of the differential equation
<br/>$${{dy} \over {dx}} = \left( {\tan x - y} \right){\sec ^2}x$$, $$x \in \left( { - {\pi \over 2},{\pi \over 2}} \right)$$,
<br/>such that y (0) = 0, then $$y\left( { - {\pi \over 4}} \right)$$ is equal to :
Options:
[{"identifier": "A", "content": "$${1... | ["B"]
Explanation:
$${{dy} \over {dx}} + y{\sec ^2}x = se{c^2}x\,tanx$$<br> $$ \to $$ This is linear
differential equation<br><br>
$$IF = {e^{\int {{{\sec }^2}xdx} }} = {e^{\tan x}}$$<br><br>
Now solution is<br><br>
$$y.{e^{\tan x}} = \int {{e^{\tan x}}} {\sec ^2}x\tan xdx$$<br><br>
$$ \therefore $$ Let tanx = t<br><b... |
Let y = y(x) be the solution of the differential equation,
<br/>$${{dy} \over {dx}} + y\tan x = 2x + {x^2}\tan x$$, $$x \in \left( { - {\pi \over 2},{\pi \over 2}} \right)$$, such that
y(0) = 1. Then :
Options:
[{"identifier": "A", "content": "$$y\\left( {{\\pi \\over 4}} \\right) - y\\left( { - {\\pi \\over 4}}... | ["B"]
Explanation:
$${{dy} \over {dx}} + y(\tan x) = 2x + {x^2}\tan x$$<br><br>
I.F. = $${e^{\int {\tan x\,dx} }}$$ = $${e^{\ln \sec x}}$$ = sec x<br><br>
y. sec x = $$\int {(2x + {x^2}\tan x)\sec \,x\,dx} $$<br><br>
$$ \Rightarrow y\sec x = {x^2}\sec x + \lambda $$<br><br>
$$ \Rightarrow $$ y(0) = 0 + $$\lambda $$ = ... |
Consider the differential equation, $${y^2}dx + \left( {x - {1 \over y}} \right)dy = 0$$, If value of y is 1 when x = 1, then the value of x
for which y = 2, is :
Options:
[{"identifier": "A", "content": "$${3 \\over 2} - {1 \\over {\\sqrt e }}$$"}, {"identifier": "B", "content": "$${1 \\over 2} + {1 \\over {\\sqrt e ... | ["A"]
Explanation:
$${y^2}dx + \left( {x - {1 \over y}} \right)dy = 0$$<br><br>
$$ \Rightarrow {{dx} \over {dy}} + {x \over {{y^2}}} = {1 \over {{y^3}}}$$<br><br>
Integrating factor (I.F) = $${e^{ - {1 \over y}}}$$<br><br>
Now x.$${e^{ - {1 \over y}}}$$ = $$\int {{e^{ - {1 \over y}}}{1 \over {{y^3}}}dy} $$ by putting ... |
Let y = y(x) be the solution of the differential
equation,
<br/>$${{2 + \sin x} \over {y + 1}}.{{dy} \over {dx}} = - \cos x$$, y > 0,y(0) = 1.<br/> If y($$\pi $$) = a and $${{dy} \over {dx}}$$ at x =
$$\pi $$ is b, then the ordered pair
(a, b) is equal to :
Options:
[{"identifier": "A", "content": "(2, 1)"}, {"ide... | ["D"]
Explanation:
$${{2 + \sin x} \over {y + 1}}.{{dy} \over {dx}} = - \cos x$$
<br><br>$$ \Rightarrow $$ $$\int {{{dy} \over {y + 1}}} = \int {{{\left( { - \cos x} \right)dx} \over {2 + \sin x}}} $$
<br><br>$$ \Rightarrow $$ $$\ln \left| {y + 1} \right| = - \ln \left| {2 + \sin x} \right| + \ln c$$
<br><br>$$ \Ri... |
Let y = y(x) be the solution of the differential
equation
<br/><br>cosx$${{dy} \over {dx}}$$ + 2ysinx = sin2x, x $$ \in $$ $$\left( {0,{\pi \over 2}} \right)$$.
<br/><br>If
y$$\left( {{\pi \over 3}} \right)$$ = 0, then y$$\left( {{\pi \over 4}} \right)$$ is equal to :</br></br>
Options:
[{"identifier": "A", "conten... | ["B"]
Explanation:
cosx$${{dy} \over {dx}}$$ + 2ysinx = sin2x
<br><br>$$ \Rightarrow $$ $${{dy} \over {dx}} + 2y\tan x = 2\sin x$$
<br><br>I.F = $${e^{\int {2\tan xdx} }}$$ = sec<sup>2</sup> x
<br><br>y.sec<sup>2</sup> x = $${\int {2\sin x{{\sec }^2}xdx} }$$
<br><br>$$ \Rightarrow $$ ysec<sup>2</sup>x = $${\int {2\tan... |
If a curve passes through the origin and the slope of the tangent to it at any point (x, y) is $${{{x^2} - 4x + y + 8} \over {x - 2}}$$, then this curve also passes through the point :
Options:
[{"identifier": "A", "content": "(4, 4)"}, {"identifier": "B", "content": "(5, 5)"}, {"identifier": "C", "content": "(5, 4)"}... | ["B"]
Explanation:
Given<br><br>y (0) = 0<br><br>& $${{dy} \over {dx}} = {{{{(x - 2)}^2} + y + 4} \over {x - 2}}$$<br><br>$$ \Rightarrow {{dy} \over {dx}} - {y \over {x - 2}} = (x - 2) + {4 \over {x - 2}}$$<br><br>$$ \Rightarrow I.F. = {e^{ - \int {{1 \over {x - 2}}dx} }} = {1 \over {x - 2}}$$<br><br>Solution of D... |
If the curve, y = y(x) represented by the solution of the differential equation (2xy<sup>2</sup> $$-$$ y)dx + xdy = 0, passes through the intersection of the lines, 2x $$-$$ 3y = 1 and 3x + 2y = 8, then |y(1)| is equal to _________.
Options:
[] | 1
Explanation:
Given, <br><br>$$(2x{y^2} - y)dx + xdx = 0$$<br><br>$$ \Rightarrow {{dy} \over {dx}} + 2{y^2} - {y \over x} = 0$$<br><br>$$ \Rightarrow - {1 \over {{y^2}}}{{dy} \over {dx}} + {1 \over y}\left( {{1 \over x}} \right) = 2$$<br><br>$${1 \over y} = z$$<br><br>$$ - {1 \over {{y^2}}}{{dy} \over {dx}} = {{dz} ... |
If y = y(x) is the solution of the equation <br/><br>$${e^{\sin y}}\cos y{{dy} \over {dx}} + {e^{\sin y}}\cos x = \cos x$$, y(0) = 0; then <br/><br>$$1 + y\left( {{\pi \over 6}} \right) + {{\sqrt 3 } \over 2}y\left( {{\pi \over 3}} \right) + {1 \over {\sqrt 2 }}y\left( {{\pi \over 4}} \right)$$ is equal to _________... | 1
Explanation:
e<sup>sin y</sup> cos y$${{dy} \over {dx}}$$ + e<sup>sin y</sup> cos x = cos x<br><br>Put e<sup>sin y</sup> = t<br><br>e<sup>sin y</sup> $$\times$$ cos y$${{dy} \over {dx}}$$ = $${{dt} \over {dx}}$$<br><br>$$ \Rightarrow $$ $${{dt} \over {dx}}$$ + t cos x = cos x<br><br>I. F. = $${e^{\int {\cos x\,dx} }... |
If y = y(x) is the solution of the differential equation, <br/><br/>$${{dy} \over {dx}} + 2y\tan x = \sin x,y\left( {{\pi \over 3}} \right) = 0$$, then the maximum value of the function y(x) over R is equal to:
Options:
[{"identifier": "A", "content": "$${1 \\over 8}$$"}, {"identifier": "B", "content": "8"}, {"identi... | ["A"]
Explanation:
$${{dy} \over {dx}} + 2\tan x.y = \sin x$$<br><br>$$I.F. = {e^{2\ln (\sec x)}} = {\sec ^2}x$$<br><br>$$y.{\sec ^2}x = \int {\sin x{{\sec }^2}xdx = \int {\tan x\sec x\,dx + c} } $$<br><br>$$y{\sec ^2}x = \sec x + c$$<br><br>$$y = \cos x + c{\cos ^2}x$$<br><br>$$x = {\pi \over 3},y = 0$$<br><br>$$ \R... |
If y = y(x) is the solution of the differential equation <br/><br/>$${{dy} \over {dx}}$$ + (tan x) y = sin x, $$0 \le x \le {\pi \over 3}$$, with y(0) = 0, then $$y\left( {{\pi \over 4}} \right)$$ equal to :
Options:
[{"identifier": "A", "content": "$${1 \\over 2}$$log<sub>e</sub> 2"}, {"identifier": "B", "content":... | ["B"]
Explanation:
Integrating Factor $$= {e^{\int {\tan x\,dx} }} = {e^{\ln (\sec x)}} = \sec x$$<br><br>$$y\sec x = \int {(\sin x)\sec x\,dx = \ln (\sec x) + C} $$<br><br>$$y(0) = 0 \Rightarrow C = 0$$<br><br>$$ \therefore $$ $$y = \cos x\ln |\sec x|$$<br><br>$$y\left( {{\pi \over 4}} \right) = {1 \over {\sqrt 2 }}... |
If the curve y = y(x) is the solution of the differential equation<br/><br/> $$2({x^2} + {x^{5/4}})dy - y(x + {x^{1/4}})dx = {2x^{9/4}}dx$$, x > 0 which <br/><br/>passes through the point $$\left( {1,1 - {4 \over 3}{{\log }_e}2} \right)$$, then the value of y(16) is equal to :
Options:
[{"identifier": "A", "content... | ["A"]
Explanation:
$${{dy} \over {dx}} - {y \over {2x}} = {{{x^{9/4}}} \over {{x^{5/4}}({x^{3/4}} + 1)}}$$<br><br>$$IF = {e^{ - \int {{{dx} \over {2x}}} }} = {e^{ - {1 \over 2}\ln x}} = {1 \over {{x^{1/2}}}}$$<br><br>$$y.{x^{ - 1/2}} = \int {{{{x^{9/4}}.{x^{ - 1/2}}} \over {{x^{5/4}}({x^{3/4}} + 1)}}} dx$$<br><br>= $$... |
Let y = y(x) be the solution of the differential equation <br/><br/>$$\cos x(3\sin x + \cos x + 3)dy = (1 + y\sin x(3\sin x + \cos x + 3))dx,0 \le x \le {\pi \over 2},y(0) = 0$$. Then, $$y\left( {{\pi \over 3}} \right)$$ is equal to :
Options:
[{"identifier": "A", "content": "$$2{\\log _e}\\left( {{{\\sqrt 3 + 7} \... | ["C"]
Explanation:
$$\cos x(3\sin x + \cos x + 3)dy = (1 + y\sin x(3\sin x + \cos x + 3))dx$$ ..... (1)<br><br>$$(3\sin x + \cos x + 3)(\cos x\,dy - y\sin x\,dx) = dx$$<br><br>$$\int {d(y.\cos x) = \int {{{dx} \over {3\sin x + \cos x + 3}}} } $$<br><br>$$y\cos x = \int {{1 \over {3\left( {{{2 + \tan {x \over 2}} \over... |
Let y = y(x) be the solution of the differential equation <br/><br/>$${{dy} \over {dx}} = (y + 1)\left( {(y + 1){e^{{x^2}/2}} - x} \right)$$, 0 < x < 2.1, with y(2) = 0. Then the value of $${{dy} \over {dx}}$$ at x = 1 is equal to :
Options:
[{"identifier": "A", "content": "$${{{e^{5/2}}} \\over {{{(1 + {e^2})}^... | ["D"]
Explanation:
$${{dy} \over {dx}} = (y + 1)\left( {(y + 1){e^{{{{x^2}} \over 2}}} - x} \right)$$<br><br>$$ \Rightarrow {{ - 1} \over {{{(y + 1)}^2}}}{{dy} \over {dx}} - x\left( {{1 \over {y + 1}}} \right) = - {e^{{{{x^2}} \over 2}}}$$<br><br>Put, $${1 \over {y + 1}} = z$$<br><br>$$ - {1 \over {{{(y + 1)}^2}}}.{{... |
Let y = y(x) satisfies the equation $${{dy} \over {dx}} - |A| = 0$$, for all x > 0, where $$A = \left[ {\matrix{
y & {\sin x} & 1 \cr
0 & { - 1} & 1 \cr
2 & 0 & {{1 \over x}} \cr
} } \right]$$. If $$y(\pi ) = \pi + 2$$, then the value of $$y\left( {{\pi \over 2}} \right)$$ ... | ["A"]
Explanation:
$$|A| = - {y \over x} + 2\sin x + 2$$<br><br>$${{dy} \over {dx}} = |A|$$<br><br>$${{dy} \over {dx}} = - {y \over x} + 2\sin x + 2$$<br><br>$${{dy} \over {dx}} + {y \over x} = 2\sin x + 2$$<br><br>$$I.F. = {e^{\int {{1 \over x}dx} }} = x$$<br><br>$$ \Rightarrow yx = \int {x(2\sin x + 2)dx} $$<br><b... |
Let y = y(x) be the solution of the differential equation $$\cos e{c^2}xdy + 2dx = (1 + y\cos 2x)\cos e{c^2}xdx$$, with $$y\left( {{\pi \over 4}} \right) = 0$$. Then, the value of $${(y(0) + 1)^2}$$ is equal to :
Options:
[{"identifier": "A", "content": "e<sup>1/2</sup>"}, {"identifier": "B", "content": "e<sup>$$-$$1... | ["C"]
Explanation:
$${{dy} \over {dx}} + 2{\sin ^2}x = 1 + y\cos 2x$$<br><br>$$ \Rightarrow {{dy} \over {dx}} + ( - \cos 2x)y = \cos 2x$$<br><br>$$I.F. = {e^{\int { - \cos 2xdx} }} = {e^{ - {{\sin 2x} \over 2}}}$$<br><br>Solution of D.E.<br><br>$$y\left( {{e^{ - {{\sin 2x} \over 2}}}} \right) = \int {(\cos 2x)\left( {... |
Let y = y(x) be solution of the following differential equation $${e^y}{{dy} \over {dx}} - 2{e^y}\sin x + \sin x{\cos ^2}x = 0,y\left( {{\pi \over 2}} \right) = 0$$ If $$y(0) = {\log _e}(\alpha + \beta {e^{ - 2}})$$, then $$4(\alpha + \beta )$$ is equal to ______________.
Options:
[] | 4
Explanation:
Let e<sup>y</sup> = t<br><br>$$ \Rightarrow {{dt} \over {dx}} - (2\sin x)t = - \sin x{\cos ^2}x$$<br><br>$$I.F. = {e^{2\cos x}}$$<br><br>$$ \Rightarrow t.{e^{2\cos x}} = \int {{e^{2\cos x}}.( - \sin x{{\cos }^2}x)dx} $$<br><br>$$ \Rightarrow {e^y}.{e^{2\cos x}} = \int {{e^{2z}}.{z^2}dz,z = {e^{2\cos x}... |
Let y = y(x) be a solution curve of the differential equation $$(y + 1){\tan ^2}x\,dx + \tan x\,dy + y\,dx = 0$$, $$x \in \left( {0,{\pi \over 2}} \right)$$. If $$\mathop {\lim }\limits_{x \to 0 + } xy(x) = 1$$, then the value of $$y\left( {{\pi \over 4}} \right)$$ is :
Options:
[{"identifier": "A", "content": "$$ -... | ["D"]
Explanation:
$$(y + 1){\tan ^2}x\,dx + \tan x\,dy + y\,dx = 0$$<br><br>or $${{dy} \over {dx}} + {{{{\sec }^2}x} \over {\tan x}}.y = - \tan x$$<br><br>$$IF = {e^{\int {{{{{\sec }^2}x} \over {\tan x}}dx} }} = {e^{\ln \tan x}} = \tan x$$<br><br>$$\therefore$$ $$y\tan x = - \int {{{\tan }^2}x\,dx} $$<br><br>or $$y... |
Let us consider a curve, y = f(x) passing through the point ($$-$$2, 2) and the slope of the tangent to the curve at any point (x, f(x)) is given by f(x) + xf'(x) = x<sup>2</sup>. Then :
Options:
[{"identifier": "A", "content": "$${x^2} + 2xf(x) - 12 = 0$$"}, {"identifier": "B", "content": "$${x^3} + xf(x) + 12 = 0$$"... | ["C"]
Explanation:
$$y + {{xdy} \over {dx}} = {x^2}$$ (given)<br><br>$$ \Rightarrow {{dy} \over {dx}} + {y \over x} = x$$<br><br>If $${e^{\int {{1 \over x}dx} }} = x$$<br><br>Solution of DE<br><br>$$ \Rightarrow y\,.\,x = \int {x\,.\,x\,dx} $$<br><br>$$ \Rightarrow xy = {{{x^3}} \over 3} + {c \over 3}$$<br><br>Passes ... |
If the solution curve of the differential equation (2x $$-$$ 10y<sup>3</sup>)dy + ydx = 0, passes through the points (0, 1) and (2, $$\beta$$), then $$\beta$$ is a root of the equation :
Options:
[{"identifier": "A", "content": "y<sup>5</sup> $$-$$ 2y $$-$$ 2 = 0"}, {"identifier": "B", "content": "2y<sup>5</sup> $$-$$... | ["D"]
Explanation:
$$(2x - 10{y^3})dy + ydx = 0$$<br><br>$$ \Rightarrow {{dx} \over {dy}} + \left( {{2 \over y}} \right)x = 10{y^2}$$<br><br>$$I.F. = {e^{\int {{2 \over y}dy} }} = {e^{2\ln (y)}} = {y^2}$$<br><br>Solution of D.E. is<br><br>$$\therefore$$ $$x\,.\,y = \int {(10{y^2}){y^2}.\,dy} $$<br><br>$$x{y^2} = {{10{... |
If $${{dy} \over {dx}} = {{{2^x}y + {2^y}{{.2}^x}} \over {{2^x} + {2^{x + y}}{{\log }_e}2}}$$, y(0) = 0, then for y = 1, the value of x lies in the interval :
Options:
[{"identifier": "A", "content": "(1, 2)"}, {"identifier": "B", "content": "$$\\left( {{1 \\over 2},1} \\right]$$"}, {"identifier": "C", "content": "(2,... | ["A"]
Explanation:
$${{dy} \over {dx}} = {{{2^x}(y + {2^y})} \over {{2^x}(1 + {2^y}\ln 2)}}$$<br><br>$$ \Rightarrow \int {{{(1 + {2^y})\ln 2} \over {(y + {2^y})}}dy = \int {dx} } $$<br><br>$$ \Rightarrow \ln \left| {y + {2^y}} \right| = x + c$$<br><br>x = 0; y = 0 $$\Rightarrow$$ c = 0<br><br>$$ \Rightarrow x = \ln \l... |
If y = y(x) is the solution curve of the differential equation $${x^2}dy + \left( {y - {1 \over x}} \right)dx = 0$$ ; x > 0 and y(1) = 1, then $$y\left( {{1 \over 2}} \right)$$ is equal to :
Options:
[{"identifier": "A", "content": "$${3 \\over 2} - {1 \\over {\\sqrt e }}$$"}, {"identifier": "B", "content": "$$3 + ... | ["D"]
Explanation:
$${x^2}dy + \left( {y - {1 \over x}} \right)dx = 0$$ ; x > 0, y(1) = 1<br><br>$${x^2}dy + {{(xy - 1)} \over x}dx = 0$$<br><br>$${x^2}dy = {{(xy - 1)} \over x}dx$$<br><br>$${{dy} \over {dx}} = {{1 - xy} \over {{x^3}}}$$<br><br>$${{dy} \over {dx}} = {1 \over {{x^3}}} - {y \over {{x^2}}}$$<br><br>$$... |
<p>Let y = y(x) be the solution of the differential equation $${{dy} \over {dx}} + {{\sqrt 2 y} \over {2{{\cos }^4}x - {{\cos }^2}x}} = x{e^{{{\tan }^{ - 1}}(\sqrt 2 \cot 2x)}},\,0 < x < {\pi \over 2}$$ with $$y\left( {{\pi \over 4}} \right) = {{{\pi ^2}} \over {32}}$$. If $$y\left( {{\pi \over 3}} \right) = {... | 2
Explanation:
$\frac{d y}{d x}+\frac{2 \sqrt{2} y}{1+\cos ^{2} 2 x}=x e^{\tan ^{-1}(\sqrt{2} \cot 2 x)}$
<br/><br/>
I.F. $=e^{\int \frac{2 \sqrt{2} d x}{1+\cos ^{2} 2 x}}=e^{\sqrt{2} \int \frac{2 \sec ^{2} 2 x}{2+\tan ^{2} 2 x} d x}$ $=e^{\tan ^{-1}\left(\frac{\tan 2 x}{\sqrt{2}}\right)}$
<br/><br/>
$\Rightarrow y \c... |
<p>Let y = y(x), x > 1, be the solution of the differential equation $$(x - 1){{dy} \over {dx}} + 2xy = {1 \over {x - 1}}$$, with $$y(2) = {{1 + {e^4}} \over {2{e^4}}}$$. If $$y(3) = {{{e^\alpha } + 1} \over {\beta {e^\alpha }}}$$, then the value of $$\alpha + \beta $$ is equal to _________.</p>
Options:
[] | 14
Explanation:
$\frac{d y}{d x}+y\left(\frac{2 x}{x-1}\right)=\frac{1}{(x-1)^{2}}$
<br/><br/>
$$
\text { I.F} =e^{\int \frac{2 x}{x-1} d x}
$$
<br/><br/>
$$
\begin{aligned}
& =e^{2 \int\left(\frac{x-1}{x-1}+\frac{1}{x-1}\right) d x} \\\\
& =e^{2 x+2 \ln (x-1)} \\\\
& =\mathrm{e}^{2 x}(\mathrm{x}-1)^{2}
\end{aligned}
... |
<p>Let the slope of the tangent to a curve y = f(x) at (x, y) be given by 2 $$\tan x(\cos x - y)$$. If the curve passes through the point $$\left( {{\pi \over 4},0} \right)$$, then the value of $$\int\limits_0^{\pi /2} {y\,dx} $$ is equal to :</p>
Options:
[{"identifier": "A", "content": "$$(2 - \\sqrt 2 ) + {\\pi \... | ["B"]
Explanation:
<p>$${{dy} \over {dx}} = 2\tan x(\cos x - y)$$</p>
<p>$$ \Rightarrow {{dy} \over {dx}} + 2\tan xy = 2\sin x$$</p>
<p>$$I.F. = {e^{\int {2\tan xdx} }} = {\sec ^2}x$$</p>
<p>$$\therefore$$ Solution of D.E. will be</p>
<p>$$y(x){\sec ^2}x = \int {2\sin x{{\sec }^2}xdx} $$</p>
<p>$$y{\sec ^2}x = 2\sec x... |
<p>Let y = y(x) be the solution of the differential equation $$x(1 - {x^2}){{dy} \over {dx}} + (3{x^2}y - y - 4{x^3}) = 0$$, $$x > 1$$, with $$y(2) = - 2$$. Then y(3) is equal to :</p>
Options:
[{"identifier": "A", "content": "$$-$$18"}, {"identifier": "B", "content": "$$-$$12"}, {"identifier": "C", "content": "$$... | ["A"]
Explanation:
<p>$${{dy} \over {dx}} + {{y(3{x^2} - 1)} \over {x(1 - {x^2})}} = {{4{x^3}} \over {x(1 - {x^2})}}$$</p>
<p>$$IF = {e^{\int {{{3{x^2} - 1} \over {x - {x^3}}}dx} }} = {e^{ - \ln |{x^3} - x|}} = {e^{ - \ln ({x^3} - x)}} = {1 \over {{x^3} - x}}$$</p>
<p>Solution of D.E. can be given by</p>
<p>$$y.\,{1 \... |
<p>If the solution curve of the differential equation <br/><br/>$$(({\tan ^{ - 1}}y) - x)dy = (1 + {y^2})dx$$ passes through the point (1, 0), then the abscissa of the point on the curve whose ordinate is tan(1), is</p>
Options:
[{"identifier": "A", "content": "2e"}, {"identifier": "B", "content": "$${2 \\over e}$$"},... | ["B"]
Explanation:
<p>$$\left( {({{\tan }^{ - 1}}y) - x} \right)dy = (1 + {y^2})dx$$</p>
<p>$${{dx} \over {dy}} + {x \over {1 + {y^2}}} = {{{{\tan }^{ - 1}}y} \over {1 + {y^2}}}$$</p>
<p>$$I.F. = {e^{\int {{1 \over {1 + {y^2}}}dy} }} = {e^{{{\tan }^{ - 1}}y}}$$</p>
<p>$$\therefore$$ Solution</p>
<p>$$x.\,{e^{{{\tan }^... |
<p>Let $$y = y(x)$$ be the solution of the differential equation $$(1 - {x^2})dy = \left( {xy + ({x^3} + 2)\sqrt {1 - {x^2}} } \right)dx, - 1 < x < 1$$, and $$y(0) = 0$$. If $$\int_{{{ - 1} \over 2}}^{{1 \over 2}} {\sqrt {1 - {x^2}} y(x)dx = k} $$, then k<sup>$$-$$1</sup> is equal to _____________.</p>
Options:
... | 320
Explanation:
<p>$$\left( {1 - {x^2}} \right)dy = \left( {xy + \left( {{x^3} + 2} \right)\sqrt {1 - {x^2}} } \right)dx$$</p>
<p>$$\therefore$$ $${{dy} \over {dx}} - {x \over {1 - {x^2}}}y = {{{x^3} + 3} \over {\sqrt {1 - {x^2}} }}$$</p>
<p>$$\therefore$$ $$I.F. = {e^{\int { - {x \over {1 - {x^2}}}dx} }} = \sqrt {1 ... |
<p>Let $$S = (0,2\pi ) - \left\{ {{\pi \over 2},{{3\pi } \over 4},{{3\pi } \over 2},{{7\pi } \over 4}} \right\}$$. Let $$y = y(x)$$, x $$\in$$ S, be the solution curve of the differential equation $${{dy} \over {dx}} = {1 \over {1 + \sin 2x}},\,y\left( {{\pi \over 4}} \right) = {1 \over 2}$$. If the sum of abscissas ... | 42
Explanation:
<p>$${{dy} \over {dx}} = {1 \over {1 + \sin 2x}}$$</p>
<p>$$ \Rightarrow dy = {{{{\sec }^2}xdx} \over {{{(1 + \tan x)}^2}}}$$</p>
<p>$$ \Rightarrow y = - {1 \over {1 + \tan x}} + c$$</p>
<p>When $$x = {\pi \over 4}$$, $$y = {1 \over 2}$$ gives c = 1</p>
<p>So $$y = {{\tan x} \over {1 + \tan x}} \Righ... |
<p>If $$y = y(x)$$ is the solution of the differential equation <br/><br/>$$x{{dy} \over {dx}} + 2y = x\,{e^x}$$, $$y(1) = 0$$ then the local maximum value <br/><br/>of the function $$z(x) = {x^2}y(x) - {e^x},\,x \in R$$ is :</p>
Options:
[{"identifier": "A", "content": "1 $$-$$ e"}, {"identifier": "B", "content": "0"... | ["D"]
Explanation:
<p>$$x{{dy} \over {dx}} + 2y = x{e^x},\,\,y(1) = 0$$</p>
<p>$${{dy} \over {dx}} + {2 \over x}y = {e^x}$$, then $${e^{\int {{2 \over x}dx} }}dx = {x^2}$$</p>
<p>$$y\,.\,{x^2} = \int {{x^2}{e^x}dx} $$</p>
<p>$$y{x^2} = {x^2}{e^x} - \int {2x{e^x}dx} $$</p>
<p>$$ = {x^2}{e^x} - 2(x{e^x} - {e^x}) + c$$</... |
<p>If the solution of the differential equation <br/><br/>$${{dy} \over {dx}} + {e^x}\left( {{x^2} - 2} \right)y = \left( {{x^2} - 2x} \right)\left( {{x^2} - 2} \right){e^{2x}}$$ satisfies $$y(0) = 0$$, then the value of y(2) is _______________.</p>
Options:
[{"identifier": "A", "content": "$$-$$1"}, {"identifier": "B... | ["C"]
Explanation:
<p>$$\because$$ $${{dy} \over {dx}} + {e^x}({x^2} - 2)y = ({x^2} - 2x)({x^2} - 2){e^{2x}}$$</p>
<p>Here, $$I.F. = {e^{\int {{e^x}({x^2} - 2)dx} }}$$</p>
<p>$$ = {e^{({x^2} - 2x){e^x}}}$$</p>
<p>$$\therefore$$ Solution of the differential equation is</p>
<p>$$y\,.\,{e^{({x^2} - 2x){e^x}}} = \int {({x... |
<p>Let $$y = y(x)$$ be the solution of the differential equation $$(x + 1)y' - y = {e^{3x}}{(x + 1)^2}$$, with $$y(0) = {1 \over 3}$$. Then, the point $$x = - {4 \over 3}$$ for the curve $$y = y(x)$$ is :</p>
Options:
[{"identifier": "A", "content": "not a critical point"}, {"identifier": "B", "content": "a point of ... | ["B"]
Explanation:
<p>$$(x + 1){{dy} \over {dx}} - y = {e^{3x}}{(x + 1)^2}$$</p>
<p>$${{dy} \over {dx}} - {y \over {x + 1}} = {e^{3x}}(x + 1)$$</p>
<p>If $${e^{ - \int {{1 \over {x + 1}}x} }} = {e^{ - \log (x + 1)}} = {1 \over {x + 1}}$$</p>
<p>$$\therefore$$ $$y\left( {{1 \over {x + 1}}} \right) = \int {{{{e^{3x}}(x ... |
<p>If x = x(y) is the solution of the differential equation <br/><br/>$$y{{dx} \over {dy}} = 2x + {y^3}(y + 1){e^y},\,x(1) = 0$$; then x(e) is equal to :</p>
Options:
[{"identifier": "A", "content": "$${e^3}({e^e} - 1)$$"}, {"identifier": "B", "content": "$${e^e}({e^3} - 1)$$"}, {"identifier": "C", "content": "$${e^2}... | ["A"]
Explanation:
$\frac{d x}{d y}-\frac{2 x}{y}=y^{2}(y+1) e^{y}$
<br/><br/>
$$
\text { If }=e^{\int-\frac{2}{y} d y}=e^{-2 \ln y}=\frac{1}{y^{2}}
$$
<br/><br/>
Solution is given by
<br/><br/>
$$
\begin{aligned}
&x \cdot \frac{1}{y^{2}}=\int y^{2}(y+1) e^{y} \cdot \frac{1}{y^{2}} d y \\\\
\Rightarrow & \frac{x}{y^{2... |
<p>The slope of the tangent to a curve $$C: y=y(x)$$ at any point $$(x, y)$$ on it is $$\frac{2 \mathrm{e}^{2 x}-6 \mathrm{e}^{-x}+9}{2+9 \mathrm{e}^{-2 x}}$$.
If $$C$$ passes through the points $$\left(0, \frac{1}{2}+\frac{\pi}{2 \sqrt{2}}\right)$$ and $$\left(\alpha, \frac{1}{2} \mathrm{e}^{2 \alpha}\right)$$, then ... | ["B"]
Explanation:
$\frac{d y}{d x}=\frac{2 e^{2 x}-6 e^{-x}+9}{2+9 e^{-2 x}}=e^{2 x}-\frac{6 e^{-x}}{2+9 e^{-2 x}}$
<br/><br/>
$$
\begin{aligned}
&\int d y=\int e^{2 x} d x-3 \int \underbrace{1+\left(\frac{3 e^{-x}}{\sqrt{2}}\right)^{2}}_{\text {put } e^{-x}=t} d x \\\\
&=\frac{e^{2 x}}{2}+3 \int \frac{d t}{1+\left(\... |
<p>If $${{dy} \over {dx}} + 2y\tan x = \sin x,\,0 < x < {\pi \over 2}$$ and $$y\left( {{\pi \over 3}} \right) = 0$$, then the maximum value of $$y(x)$$ is :</p>
Options:
[{"identifier": "A", "content": "$${1 \\over 8}$$"}, {"identifier": "B", "content": "$${3 \\over 4}$$"}, {"identifier": "C", "content": "$${1... | ["A"]
Explanation:
<p>$${{dy} \over {dx}} + 2y\tan x = \sin x$$</p>
<p>which is a first order linear differential equation.</p>
<p>Integrating factor (I. F.) $$ = {e^{\int {2\tan x\,dx} }}$$</p>
<p>$$ = {e^{2\ln |\sec x|}} = {\sec ^2}x$$</p>
<p>Solution of differential equation can be written as</p>
<p>$$y\,.\,{\sec ^... |
<p>Let the solution curve $$y=f(x)$$ of the differential equation $$
\frac{d y}{d x}+\frac{x y}{x^{2}-1}=\frac{x^{4}+2 x}{\sqrt{1-x^{2}}}$$, $$x\in(-1,1)$$ pass through the origin. Then $$\int\limits_{-\frac{\sqrt{3}}{2}}^{\frac{\sqrt{3}}{2}} f(x) d x
$$ is equal to</p>
Options:
[{"identifier": "A", "content": "$$\\... | ["B"]
Explanation:
<p>$${{dy} \over {dx}} + {{xy} \over {{x^2} - 1}} = {{{x^4} + 2x} \over {\sqrt {1 - {x^2}} }}$$</p>
<p>which is first order linear differential equation.</p>
<p>Integrating factor $$(I.F.) = {e^{\int {{x \over {{x^2} - 1}}dx} }}$$</p>
<p>$$ = {e^{{1 \over 2}\ln |{x^2} - 1|}} = \sqrt {|{x^2} - 1|} $$... |
<p>Suppose $$y=y(x)$$ be the solution curve to the differential equation $$\frac{d y}{d x}-y=2-e^{-x}$$ such that $$\lim\limits_{x \rightarrow \infty} y(x)$$ is finite. If $$a$$ and $$b$$ are respectively the $$x$$ - and $$y$$-intercepts of the tangent to the curve at $$x=0$$, then the value of $$a-4 b$$ is equal to _... | 3
Explanation:
<p>IF $$ = {e^{-x}}$$</p>
<p>$$y\,.\,{e^{-x}} = - 2{e^{ - x}} + {{{e^{ - 2x}}} \over 2} + C$$</p>
<p>$$ \Rightarrow y = - 2 + {e^{ - x}} + C{e^x}$$</p>
<p>$$\mathop {\lim }\limits_{x \to \infty } \,y(x)$$ is finite so $$C = 0$$</p>
<p>$$y = - 2 + {e^{ - x}}$$</p>
<p>$$ \Rightarrow {\left. {{{dy} \ove... |
<p>Let $$y=y_{1}(x)$$ and $$y=y_{2}(x)$$ be two distinct solutions of the differential equation $$\frac{d y}{d x}=x+y$$, with $$y_{1}(0)=0$$ and $$y_{2}(0)=1$$ respectively. Then, the number of points of intersection of $$y=y_{1}(x)$$ and $$y=y_{2}(x)$$ is</p>
Options:
[{"identifier": "A", "content": "0"}, {"identifie... | ["A"]
Explanation:
<p>$${{dy} \over {dx}} = x + y$$</p>
<p>Let $$x + y = t$$</p>
<p>$$1 + {{dy} \over {dx}} = {{dt} \over {dx}}$$</p>
<p>$${{dt} \over {dx}} - 1 = t \Rightarrow \int {{{dt} \over {t + 1}} = \int {dx} } $$</p>
<p>$$\ln |t + 1| = x + C'$$</p>
<p>$$|t + 1| = C{e^x}$$</p>
<p>$$|x + y + 1| = C{e^x}$$</p>
<p... |
<p>Let $$y=y(x)$$ be the solution curve of the differential equation</p>
<p>$$\sin \left( {2{x^2}} \right){\log _e}\left( {\tan {x^2}} \right)dy + \left( {4xy - 4\sqrt 2 x\sin \left( {{x^2} - {\pi \over 4}} \right)} \right)dx = 0$$, $$0 < x < \sqrt {{\pi \over 2}} $$, which passes through the point $$\left(\sqr... | 1
Explanation:
<p>$${{dy} \over {dx}} + y\left( {{{4x} \over {\sin (2{x^2})\ln (\tan {x^2})}}} \right) = {{4\sqrt 2 x\sin \left( {{x^2} - {\pi \over 4}} \right)} \over {\sin (2{x^2})\ln (\tan {x^2})}}$$</p>
<p>$$I.F = {e^{\int {{{4x} \over {\sin (2{x^2})\ln (\tan {x^2})}}dx} }}$$</p>
<p>$$ = {e^{\ln |\ln (\tan {x^2})... |
<p>Let $$y=y(x)$$ be the solution curve of the differential equation $$
\frac{d y}{d x}+\frac{1}{x^{2}-1} y=\left(\frac{x-1}{x+1}\right)^{1 / 2}$$, $$x >1$$ passing through the point $$\left(2, \sqrt{\frac{1}{3}}\right)$$. Then $$\sqrt{7}\, y(8)$$ is equal to :</p>
Options:
[{"identifier": "A", "content": "$$11+6 ... | ["D"]
Explanation:
<p>$${{dy} \over {dx}} + {1 \over {{x^2} - 1}}y = \sqrt {{{x - 1} \over {x + 1}}} ,\,x > 1$$</p>
<p>Integrating factor I.F. $$ = {e^{\int {{1 \over {{x^2} - 1}}dx} }} = {e^{{1 \over 2}\ln \left| {{{x - 1} \over {x + 1}}} \right|}}$$</p>
<p>$$ = \sqrt {{{x - 1} \over {x + 1}}} $$</p>
<p>Solution of d... |
<p>Let the solution curve $$y=y(x)$$ of the differential equation $$\left(1+\mathrm{e}^{2 x}\right)\left(\frac{\mathrm{d} y}{\mathrm{~d} x}+y\right)=1$$ pass through the point $$\left(0, \frac{\pi}{2}\right)$$. Then, $$\lim\limits_{x \rightarrow \infty} \mathrm{e}^{x} y(x)$$ is equal to :</p>
Options:
[{"identifier": ... | ["B"]
Explanation:
<p>D.E. $$(1 + {e^{2x}})\left( {{{dy} \over {dx}} + y} \right) = 1$$</p>
<p>$$ \Rightarrow {{dy} \over {dx}} + y = {1 \over {1 + {e^{2x}}}}$$</p>
<p>I.F. $$ = {e^{\int {1\,.\,dx} }} = {e^x}$$</p>
<p>$$\therefore$$ Solution</p>
<p>$${e^x}y(x) = \int {{{{e^x}} \over {1 + {e^{2x}}}}dx} $$</p>
<p>$$ \Ri... |
<p>Let $$\alpha x=\exp \left(x^{\beta} y^{\gamma}\right)$$ be the solution of the differential equation $$2 x^{2} y \mathrm{~d} y-\left(1-x y^{2}\right) \mathrm{d} x=0, x > 0,y(2)=\sqrt{\log _{e} 2}$$. Then $$\alpha+\beta-\gamma$$ equals :</p>
Options:
[{"identifier": "A", "content": "1"}, {"identifier": "B", "cont... | ["A"]
Explanation:
$\begin{aligned} & 2 x^2 y d y-\left(1-x y^2\right) d x=0 \\\\ & \Rightarrow 2 x^2 y \frac{d y}{d x}-1+x y^2=0 \\\\ & \Rightarrow 2 y \frac{d y}{d x}-\frac{1}{x^2}+\frac{y^2}{x}=0 \\\\ & \Rightarrow 2 y \frac{d y}{d x}+\frac{y^2}{x}=\frac{1}{x^2} \text { (L.D.E) } \\\\ & Let, y^2=t \Rightarrow 2 y \... |
<p>If $$y=y(x)$$ is the solution curve of the differential equation <br/><br/>$$\frac{d y}{d x}+y \tan x=x \sec x, 0 \leq x \leq \frac{\pi}{3}, y(0)=1$$, then $$y\left(\frac{\pi}{6}\right)$$ is equal to</p>
Options:
[{"identifier": "A", "content": "$$\\frac{\\pi}{12}-\\frac{\\sqrt{3}}{2} \\log _{e}\\left(\\frac{2 \\sq... | ["D"]
Explanation:
$\frac{d y}{d x}+y \tan x=x \sec x$
<br/><br/>$\therefore $ I.F $=e^{\int \tan x d x}=\sec x$
<br/><br/>$\Rightarrow y \sec x=\int x \sec ^{2} x d x$
<br/><br/>$\Rightarrow y \sec x=x \tan x-\ln |\sec x|+c$
<br/><br/>Given, $$
y(0)=1
$$
<br/><br/>$\Rightarrow 1=c$
<br/><br/>$$ \therefore $$ $... |
<p>Let the solution curve $$y=y(x)$$ of the differential equation <br/><br/>$$
\frac{\mathrm{d} y}{\mathrm{~d} x}-\frac{3 x^{5} \tan ^{-1}\left(x^{3}\right)}{\left(1+x^{6}\right)^{3 / 2}} y=2 x \exp \left\{\frac{x^{3}-\tan ^{-1} x^{3}}{\sqrt{\left(1+x^{6}\right)}}\right\} \text { pass through the origin. Then } y(1) \t... | ["B"]
Explanation:
<p>$${{dy} \over {dx}} - {{3{x^5}{{\tan }^{ - 1}}({x^3})} \over {{{(1 + {x^6})}^{{3 \over 2}}}}}y = 2x\exp \left\{ {{{{x^3} - {{\tan }^{ - 1}}{x^3}} \over {\sqrt {1 + {x^6}} }}} \right\}$$</p>
<p>$$IF = {e^{ - \int {{{3{x^5}{{\tan }^{ - 1}}({x^3})} \over {{{(1 + {x^6})}^{{3 \over 2}}}}}dx} }}$$</p>
... |
<p>Let $$y=y(x)$$ be the solution of the differential equation $$x{\log _e}x{{dy} \over {dx}} + y = {x^2}{\log _e}x,(x > 1)$$. If $$y(2) = 2$$, then $$y(e)$$ is equal to</p>
Options:
[{"identifier": "A", "content": "$${{1 + {e^2}} \\over 2}$$"}, {"identifier": "B", "content": "$${{1 + {e^2}} \\over 4}$$"}, {"identi... | ["D"]
Explanation:
<p>$$x\ln x{{dy} \over {dx}} + y = {x^2}\ln x$$</p>
<p>$${{dy} \over {dx}} + {1 \over {x\ln x}}\,.\,y = x$$</p>
<p>If $$ = {e^{\int {{1 \over {x\ln x}}dx} }} = {e^{\int {{1 \over t}dt} }}$$, where $$t = \ln x$$</p>
<p>$$ = {e^{\ln t}} = t = \ln x$$</p>
<p>$$y.\ln x = \int {x\ln x = {{{x^2}} \over 2}... |
<p>Let $$y=y(t)$$ be a solution of the differential equation $${{dy} \over {dt}} + \alpha y = \gamma {e^{ - \beta t}}$$ where, $$\alpha > 0,\beta > 0$$ and $$\gamma > 0$$. Then $$\mathop {\lim }\limits_{t \to \infty } y(t)$$</p>
Options:
[{"identifier": "A", "content": "is 0"}, {"identifier": "B", "content... | ["A"]
Explanation:
$\frac{d y}{d t}+\alpha y=\gamma e^{-\beta t}$
<br/><br/>
$$
\begin{aligned}
& \text { I.F. }=e^{\int \alpha d t}=e^{\alpha t} \\\\
& \Rightarrow y \cdot e^{\alpha t}=\gamma \int e^{(\alpha-\beta) t} d t=\gamma \frac{e^{(\alpha-\beta) t}}{(\alpha-\beta)}+C \\\\
& \Rightarrow y=\frac{\gamma}{(\alpha-... |
<p>Let $$y = y(x)$$ be the solution curve of the differential equation $${{dy} \over {dx}} = {y \over x}\left( {1 + x{y^2}(1 + {{\log }_e}x)} \right),x > 0,y(1) = 3$$. Then $${{{y^2}(x)} \over 9}$$ is equal to :</p>
Options:
[{"identifier": "A", "content": "$${{{x^2}} \\over {5 - 2{x^3}(2 + {{\\log }_e}{x^3})}}$$"}... | ["A"]
Explanation:
$$
\begin{aligned}
& \frac{d y}{d x}-\frac{y}{x}=y^3\left(1+\log _e x\right) \\\\
& \frac{1}{y^3} \frac{d y}{d x}-\frac{1}{x y^2}=1+\log _e x \\\\
& \text { Let }-\frac{1}{y^2}=t \Rightarrow \frac{2}{y^3} \frac{d y}{d x}=\frac{d t}{d x} \\\\
& \therefore \frac{d t}{d x}+\frac{2 t}{x}=2\left(1+\log _... |
<p>Let $$y = y(x)$$ be the solution of the differential equation $${x^3}dy + (xy - 1)dx = 0,x > 0,y\left( {{1 \over 2}} \right) = 3 - \mathrm{e}$$. Then y (1) is equal to</p>
Options:
[{"identifier": "A", "content": "2 $$-$$ e"}, {"identifier": "B", "content": "3"}, {"identifier": "C", "content": "1"}, {"identifier... | ["C"]
Explanation:
$x^{3} d y+x y d x-d x=0$
<br/><br/>
$\Rightarrow \frac{d y}{d x}=\frac{1-x y}{x^{3}}$
<br/><br/>
$\Rightarrow \frac{d y}{d x}+\frac{y}{x^{2}}=\frac{1}{x^{3}}$
<br/><br/>
I.F. $=e^{\int \frac{d x}{x^{2}}}=e^{-\frac{1}{x}}$
<br/><br/>
$\therefore \quad y e^{-\frac{1}{x}}=\int \frac{e^{-\frac{1}{x}}}{... |
Let $x=x(y)$ be the solution of the differential equation
<br/><br/>$2(y+2) \log _{e}(y+2) d x+\left(x+4-2 \log _{e}(y+2)\right) d y=0, y>-1$
<br/><br/>with $x\left(e^{4}-2\right)=1$. Then $x\left(e^{9}-2\right)$ is equal to :
Options:
[{"identifier": "A", "content": "$\\frac{4}{9}$"}, {"identifier": "B", "conten... | ["B"]
Explanation:
$$
\begin{aligned}
& 2(y+2) \ln (y+2) d x+(x+4-2 \ln (y+2)) d y=0 \\\\
& 2 \ln (y+2)+(x+4-2 \ln (y+2)) \frac{1}{y+2} \cdot \frac{d y}{d x}=0 \\\\
& \text { let, } \ln (y+2)=t \\\\
& \frac{1}{y+2} \cdot \frac{d y}{d x}=\frac{d t}{d x} \\\\
& 2 t+(x+4-2 t) \cdot \frac{d t}{d x}=0 \\\\
& (x+4-2 t) \fra... |
<p>If $$y=y(x)$$ is the solution of the differential equation <br/><br/>$$\frac{d y}{d x}+\frac{4 x}{\left(x^{2}-1\right)} y=\frac{x+2}{\left(x^{2}-1\right)^{\frac{5}{2}}}, x > 1$$ such that <br/><br/>$$y(2)=\frac{2}{9} \log _{e}(2+\sqrt{3}) \text { and } y(\sqrt{2})=\alpha \log _{e}(\sqrt{\alpha}+\beta)+\beta-\sqrt... | 6
Explanation:
<p>We can solve the given differential equation using an integrating factor.
<br/><br/>The integrating factor is given by :
<br/><br/>$$
\mu(x) = e^{\int \frac{4x}{x^2 - 1} dx} = e^{2\ln(x^2 - 1)} = (x^2 - 1)^2
$$
<br/><br/>Multiplying both sides of the differential equation by $\mu(x)$, we get :</p>
... |
<p>Let $$y=y(x), y > 0$$, be a solution curve of the differential equation $$\left(1+x^{2}\right) \mathrm{d} y=y(x-y) \mathrm{d} x$$. If $$y(0)=1$$ and $$y(2 \sqrt{2})=\beta$$, then</p>
Options:
[{"identifier": "A", "content": "$$e^{\\beta^{-1}}=e^{-2}(3+2 \\sqrt{2})$$"}, {"identifier": "B", "content": "$$e^{3 \\be... | ["C"]
Explanation:
$$
\begin{aligned}
& \left(1+x^2\right) d y=y(x-y) d x \\\\
& y(0)=1 \cdot y(2 \sqrt{2})=\beta \\\\
& \frac{d y}{d x}=\frac{y x-y^2}{1+x^2} \\\\
& \frac{d y}{d x}+y\left(\frac{-x}{1+x^2}\right)=\left(\frac{-1}{1+x^2}\right) y^2 \\\\
& \frac{1}{y^2} \frac{d y}{d x}+\frac{1}{y}\left(\frac{-x}{1+x^2}\r... |
<p>Let $$f$$ be a differentiable function such that $${x^2}f(x) - x = 4\int\limits_0^x {tf(t)dt} $$, $$f(1) = {2 \over 3}$$. Then $$18f(3)$$ is equal to :</p>
Options:
[{"identifier": "A", "content": "160"}, {"identifier": "B", "content": "210"}, {"identifier": "C", "content": "150"}, {"identifier": "D", "content": "1... | ["A"]
Explanation:
Given that
<br/><br/>$$
x^2 f(x)-x=4 \int_0^x t f(t) d t
$$
<br/><br/>On differentiating both sides with respect to $x$, we get
<br/><br/>$$
\begin{array}{rlrl}
& 2 x f(x)+x^2 f^{\prime}(x)-1 =4 x f(x) \\\\
&\Rightarrow x^2 f^{\prime}(x)-2 x f(x)-1 =0 \\\\
&\Rightarrow x^2 \frac{d y}{d x}-2 x... |
<p>Let the solution curve $$x=x(y), 0 < y < \frac{\pi}{2}$$, of the differential equation $$\left(\log _{e}(\cos y)\right)^{2} \cos y \mathrm{~d} x-\left(1+3 x \log _{e}(\cos y)\right) \sin \mathrm{y} d y=0$$ satisfy $$x\left(\frac{\pi}{3}\right)=\frac{1}{2 \log _{e} 2}$$. If $$x\left(\frac{\pi}{6}\right)=\frac{1... | 12
Explanation:
$$
\begin{aligned}
& (\cos y)(\ln (\cos y))^2 d x=(1+3 x \ln \cos y) \sin y d y \\\\
& \Rightarrow \frac{d x}{d y}=\frac{(1+3 x \ln \cos y) \sin y}{(\ln \cos y)^2 \cos y} \\\\
& =\tan y\left[\frac{1}{(\ln \cos y)^2}+\frac{3 x}{\ln \cos y}\right] \\\\
& \Rightarrow \frac{d x}{d y}-\left(\frac{3 \tan y}{... |
<p>If the solution curve of the differential equation $$\left(y-2 \log _{e} x\right) d x+\left(x \log _{e} x^{2}\right) d y=0, x > 1$$ passes through the points $$\left(e, \frac{4}{3}\right)$$ and $$\left(e^{4}, \alpha\right)$$, then $$\alpha$$ is equal to ____________.</p>
Options:
[] | 3
Explanation:
The given differential equation is,
<br/><br/>$$
\begin{aligned}
& (y-2 \log x) d x+\left(x \log x^2\right) d y=0 \\\\
& \Rightarrow \frac{d y}{d x}=\frac{(2 \log x-y)}{2 x \log x} \\\\
& \Rightarrow \frac{d y}{d x}+\frac{y}{2 x \log x}=\frac{1}{x}
\end{aligned}
$$
<br/><br/>It is a linear differential ... |
<p>Let $$y=y(x)$$ be a solution of the differential equation $$(x \cos x) d y+(x y \sin x+y \cos x-1) d x=0,0 < x < \frac{\pi}{2}$$. If $$\frac{\pi}{3} y\left(\frac{\pi}{3}\right)=\sqrt{3}$$, then $$\left|\frac{\pi}{6} y^{\prime \prime}\left(\frac{\pi}{6}\right)+2 y^{\prime}\left(\frac{\pi}{6}\right)\right|$$ is ... | 2
Explanation:
Given, differential equation
<br/><br/>$$
\begin{aligned}
& (x \cos x) d y+(x y \sin x+y \cos x-1) d x=0,0 < x < \frac{\pi}{2} \\\\
& \Rightarrow \frac{d y}{d x}+\frac{x y \sin x+y \cos x-1}{x \cos x}=0 \\\\
& \Rightarrow \frac{d y}{d x}+\left(\frac{x y \sin x+y \cos x}{x \cos x}\right)=\frac{1}{x \cos ... |
Let $\alpha$ be a non-zero real number. Suppose $f: \mathbf{R} \rightarrow \mathbf{R}$ is a differentiable function such that $f(0)=2$ and $\lim\limits_{x \rightarrow-\infty} f(x)=1$. If $f^{\prime}(x)=\alpha f(x)+3$, for all $x \in \mathbf{R}$, then $f\left(-\log _{\mathrm{e}} 2\right)$ is equal to :
Options:
[{"iden... | ["B"]
Explanation:
$$
\begin{aligned}
& f(0)=2, \lim _{x \rightarrow-\infty} f(x)=1 \\\\
& f^{\prime}(x)-x \cdot f(x)=3 \\\\
& \text { I.F }=e^{-\alpha x} \\\\
& y\left(e^{-\alpha x}\right)=\int 3 \cdot e^{-\alpha x} d x \\\\
& f(x) \cdot\left(e^{-\alpha x}\right)=\frac{3 e^{-\alpha x}}{-\alpha}+c \\\\
& x=0 \Rightarr... |
If $x=x(t)$ is the solution of the differential equation $(t+1) \mathrm{d} x=\left(2 x+(t+1)^4\right) \mathrm{dt}, x(0)=2$, then, $x(1)$ equals _________.
Options:
[] | 14
Explanation:
$\begin{aligned} & (\mathrm{t}+1) \mathrm{dx}=\left(2 \mathrm{x}+(\mathrm{t}+1)^4\right) \mathrm{dt} \\\\ & \frac{\mathrm{dx}}{\mathrm{dt}}=\frac{2 \mathrm{x}+(\mathrm{t}+1)^4}{\mathrm{t}+1} \\\\ & \frac{\mathrm{dx}}{\mathrm{dt}}-\frac{2 \mathrm{x}}{\mathrm{t}+1}=(\mathrm{t}+1)^3\end{aligned}$
<br/><br... |
Let $x=x(\mathrm{t})$ and $y=y(\mathrm{t})$ be solutions of the differential equations $\frac{\mathrm{d} x}{\mathrm{dt}}+\mathrm{a} x=0$ and $\frac{\mathrm{d} y}{\mathrm{dt}}+\mathrm{by}=0$ respectively, $\mathrm{a}, \mathrm{b} \in \mathbf{R}$. Given that $x(0)=2 ; y(0)=1$ and $3 y(1)=2 x(1)$, the value of $\mathrm{t}$... | ["B"]
Explanation:
<p>$$\begin{aligned}
& \frac{\mathrm{dx}}{\mathrm{dt}}+\mathrm{ax}=0 \\
& \frac{\mathrm{dx}}{\mathrm{x}}=-\mathrm{adt} \\
& \int \frac{\mathrm{dx}}{\mathrm{x}}=-\mathrm{a} \int \mathrm{dt} \\
& \ln |\mathrm{x}|=-\mathrm{at}+\mathrm{c} \\
& \mathrm{at} \mathrm{t}=0, \mathrm{x}=2 \\
& \ln 2=0+\mathrm{... |
<p>The temperature $$T(t)$$ of a body at time $$t=0$$ is $$160^{\circ} \mathrm{F}$$ and it decreases continuously as per the differential equation $$\frac{d T}{d t}=-K(T-80)$$, where $$K$$ is a positive constant. If $$T(15)=120^{\circ} \mathrm{F}$$, then $$T(45)$$ is equal to</p>
Options:
[{"identifier": "A", "content... | ["A"]
Explanation:
<p>$$\begin{aligned}
& \frac{\mathrm{dT}}{\mathrm{dt}}=-\mathrm{k}(\mathrm{T}-80) \\
& \int_\limits{160}^{\mathrm{T}} \frac{\mathrm{dT}}{(\mathrm{T}-80)}=\int_\limits0^{\mathrm{t}}-\mathrm{Kdt} \\
& {[\ln |\mathrm{T}-80|]_{160}^{\mathrm{T}}=-\mathrm{kt}} \\
& \ln |\mathrm{T}-80|-\ln 80=-\mathrm{kt} ... |
<p>A function $$y=f(x)$$ satisfies $$f(x) \sin 2 x+\sin x-\left(1+\cos ^2 x\right) f^{\prime}(x)=0$$ with condition $$f(0)=0$$. Then, $$f\left(\frac{\pi}{2}\right)$$ is equal to</p>
Options:
[{"identifier": "A", "content": "2"}, {"identifier": "B", "content": "1"}, {"identifier": "C", "content": "$$-$$1"}, {"identifie... | ["B"]
Explanation:
<p>$$\begin{aligned}
& \frac{d y}{d x}-\left(\frac{\sin 2 x}{1+\cos ^2 x}\right) y=\sin x \\
& \text { I.F. }=1+\cos ^2 x \\
& y \cdot\left(1+\cos ^2 x\right)=\int(\sin x) d x \\
& =-\cos x+C \\
& x=0, C=1 \\
& y\left(\frac{\pi}{2}\right)=1
\end{aligned}$$</p> |
<p>Let $$y=y(x)$$ be the solution of the differential equation $$\left(1-x^2\right) \mathrm{d} y=\left[x y+\left(x^3+2\right) \sqrt{3\left(1-x^2\right)}\right] \mathrm{d} x, -1< x<1, y(0)=0$$. If $$y\left(\frac{1}{2}\right)=\frac{\mathrm{m}}{\mathrm{n}}, \mathrm{m}$$ and $$\mathrm{n}$$ are co-prime numbers, then ... | 97
Explanation:
<p>$$\begin{aligned}
& \frac{d y}{d x}-\frac{x y}{1-x^2}=\frac{\left(x^3+2\right) \sqrt{3\left(1-x^2\right)}}{1-x^2} \\
& \mathrm{IF}=e^{-\int \frac{x}{1-x^2} d x}=e^{+\frac{1}{2} \ln \left(1-x^2\right)}=\sqrt{1-x^2} \\
& y \sqrt{1-x^2}=\sqrt{3} \int\left(x^3+2\right) d x \\
& y \sqrt{1-x^2}=\sqrt{3}\l... |
<p>Let $$\int_\limits0^x \sqrt{1-\left(y^{\prime}(t)\right)^2} d t=\int_0^x y(t) d t, 0 \leq x \leq 3, y \geq 0, y(0)=0$$. Then at $$x=2, y^{\prime \prime}+y+1$$ is equal to</p>
Options:
[{"identifier": "A", "content": "$$\\sqrt2$$"}, {"identifier": "B", "content": "2"}, {"identifier": "C", "content": "1/2"}, {"identi... | ["D"]
Explanation:
<p>$$\int_\limits0^x \sqrt{1-\left(y^{\prime}(t)\right)^2} d t=\int_\limits0^x y(t) d t$$</p>
<p>Differentiating both side</p>
<p>$$\begin{aligned}
& \sqrt{1-\left(y^{\prime}(x)\right)^2}=y(x) \\
& \left(\frac{d y}{d x}\right)^2+y^2=1 \\
& y^{\prime 2}+y^2=1 \\
& 2 y^{\prime} y^{\pri... |
<p>For a differentiable function $$f: \mathbb{R} \rightarrow \mathbb{R}$$, suppose $$f^{\prime}(x)=3 f(x)+\alpha$$, where $$\alpha \in \mathbb{R}, f(0)=1$$ and $$\lim _\limits{x \rightarrow-\infty} f(x)=7$$. Then $$9 f\left(-\log _e 3\right)$$ is equal to _________.</p>
Options:
[] | 61
Explanation:
<p>$$\begin{aligned}
& f^{\prime}(x)=3 f(x)+\alpha \\
& \Rightarrow \frac{d y}{3 y+\alpha}=d x \\
& \Rightarrow \frac{1}{3} \ln (3 y+\alpha)=x+C \\
& y(0)=1 \Rightarrow C=\frac{1}{3} \ln (3+\alpha) \\
& \frac{1}{3} \ln \left(\frac{3 y+\alpha}{3+\alpha}\right)=x \\
& \Rightarrow y=\frac{1}{3}\left((3+\a... |
<p>The solution of the differential equation $$(x^2+y^2) \mathrm{d} x-5 x y \mathrm{~d} y=0, y(1)=0$$, is :</p>
Options:
[{"identifier": "A", "content": "$$\\left|x^2-4 y^2\\right|^5=x^2$$\n"}, {"identifier": "B", "content": "$$\\left|x^2-2 y^2\\right|^6=x$$\n"}, {"identifier": "C", "content": "$$\\left|x^2-2 y^2\\rig... | ["A"]
Explanation:
<p>$$\begin{aligned}
& \left(x^2+y^2\right) d x-5 x y d y=0 \\
& \frac{d y}{d x}=\frac{x^2+y^2}{5 x y} \\
& \text { Let } y=v x \\
& \frac{d y}{d x}=v+x \frac{d v}{d x} \\
& V+x \frac{d v}{d x}=\frac{1+v^2}{5 v} \\
& x \frac{d v}{d x}=\frac{1+v^2-5 v^2}{5 v}
\end{aligned}$$</p>
<p>$$\begin{aligned}
... |
<p>The solution curve, of the differential equation $$2 y \frac{\mathrm{d} y}{\mathrm{~d} x}+3=5 \frac{\mathrm{d} y}{\mathrm{~d} x}$$, passing through the point $$(0,1)$$ is a conic, whose vertex lies on the line :</p>
Options:
[{"identifier": "A", "content": "$$2 x+3 y=-9$$\n"}, {"identifier": "B", "content": "$$2 x+... | ["C"]
Explanation:
<p>$$\begin{aligned}
& 2 y \frac{d y}{d x}+3=5 \frac{d y}{d x} \\
& 2 y d y+3 d x=5 d y \\
& y^2+3 x=5 y+\left.c\right|_{(0,1)} \\
& 1+0=5+c \\
& c=-4 \\
& y^2-5 y=-3 x-4 \\
& y^2-5 y+\frac{25}{4}-\frac{25}{4}=-3 x-4 \\
& \left(y-\frac{5}{2}\right)^2=-3 x+\frac{9}{4} \\
& \left(y-\frac{5}{2}\right)^... |
<p>Let the solution $$y=y(x)$$ of the differential equation $$\frac{\mathrm{d} y}{\mathrm{~d} x}-y=1+4 \sin x$$ satisfy $$y(\pi)=1$$. Then $$y\left(\frac{\pi}{2}\right)+10$$ is equal to __________.</p>
Options:
[] | 7
Explanation:
<p>$$\begin{aligned}
& \frac{d y}{d x}-y=1+4 \sin x \\
& \text { Integrating factor }=e^{-\int d x}=e^{-x}
\end{aligned}$$</p>
<p>Solution is $$y e^{-x}=\int(1+4 \sin x) e^{-x} d x$$</p>
<p>$$\begin{aligned}
& =-e^{-x}+2 \cdot e^{-x}(-\sin x-\cos x)+C \\
y(\pi) & =1 \Rightarrow C=0
\end{aligned}$$</p>
<... |
<p>If $$y=y(x)$$ is the solution of the differential equation $$\frac{\mathrm{d} y}{\mathrm{~d} x}+2 y=\sin (2 x), y(0)=\frac{3}{4}$$, then $$y\left(\frac{\pi}{8}\right)$$ is equal to :</p>
Options:
[{"identifier": "A", "content": "$$\\mathrm{e}^{-\\pi / 8}$$\n"}, {"identifier": "B", "content": "$$\\mathrm{e}^{\\pi / ... | ["C"]
Explanation:
<p>$$\begin{aligned}
& \frac{d y}{d x}+2 y=\sin 2 x \\
& \text { IF }=e^{2 d x}=e^{2 x} \\
& y \cdot e^{2 x}=\int e^{2 x} \sin 2 x d x+c \\
& =\frac{e^{2 x}}{8}(2 \sin 2 x-2 \cos 2 x)+c \\
& y(0)=\frac{3}{4} \\
& \frac{3}{4}=\frac{1}{8}(-2)+c \Rightarrow c=1 \\
& \text { Put } x=\frac{\pi}{8} \\
& y... |
<p>Let $$y=y(x)$$ be the solution of the differential equation</p>
<p>$$\frac{\mathrm{d} y}{\mathrm{~d} x}+\frac{2 x}{\left(1+x^2\right)^2} y=x \mathrm{e}^{\frac{1}{\left(1+x^2\right)}} ; y(0)=0.$$</p>
<p>Then the area enclosed by the curve $$f(x)=y(x) \mathrm{e}^{-\frac{1}{\left(1+x^2\right)}}$$ and the line $$y-x=4$$... | 18
Explanation:
<p>$$\frac{d y}{d x}+\frac{2 x}{\left(1+x^2\right)^2} y=x e^{\frac{1}{1+x^2}} ; y(0)=0$$</p>
<p>I.F. of linear differential equation,</p>
<p>$$\begin{aligned}
& \text { I.F. }=e^{\int \frac{2 x}{\left(1+x^2\right)^2}} d x=e^{\left(\frac{-1}{1+x^2}\right)} \\
& \Rightarrow y\left(e^{\left(\frac{-1}{1+x^... |
<p>Let $$y=y(x)$$ be the solution of the differential equation $$\left(2 x \log _e x\right) \frac{d y}{d x}+2 y=\frac{3}{x} \log _e x, x>0$$ and $$y\left(e^{-1}\right)=0$$. Then, $$y(e)$$ is equal to </p>
Options:
[{"identifier": "A", "content": "$$-\\frac{3}{\\mathrm{e}}$$\n"}, {"identifier": "B", "content": "$$-\... | ["A"]
Explanation:
<p>$$\begin{aligned}
& (2 x \log x) \frac{d y}{d x}+2 y=\frac{3}{x} \log x \\
& \frac{d y}{d x}+\frac{y}{x \log x}=\frac{3}{2 x^2} \\
& I F=e^{\int \frac{1}{x \log x}}=e^{\log (\log x)}=\log x \\
& y \times \log x=\int \log x \times \frac{3}{2 x^2} d x+C \\
& y \log x=\frac{3}{2}\left[\frac{-\log x}... |
<p>Let $$y=y(x)$$ be the solution of the differential equation $$\left(1+x^2\right) \frac{d y}{d x}+y=e^{\tan ^{-1} x}$$, $$y(1)=0$$. Then $$y(0)$$ is</p>
Options:
[{"identifier": "A", "content": "$$\\frac{1}{4}\\left(e^{\\pi / 2}-1\\right)$$\n"}, {"identifier": "B", "content": "$$\\frac{1}{2}\\left(1-e^{\\pi / 2}\\ri... | ["B"]
Explanation:
<p>To determine $ y(0) $, we start by solving the differential equation given:</p>
<p>$ (1 + x^2) \frac{dy}{dx} + y = e^{\tan^{-1} x} $</p>
<p>First, we rewrite it in the standard form for a linear differential equation:</p>
<p>$ \frac{dy}{dx} + \frac{y}{1 + x^2} = \frac{e^{\tan^{-1} x}}{1 + x^2}... |
The order and degree of the differential equation
<br/>$$\,{\left( {1 + 3{{dy} \over {dx}}} \right)^{2/3}} = 4{{{d^3}y} \over {d{x^3}}}$$ are
Options:
[{"identifier": "A", "content": "$$\\left( {1,{2 \\over 3}} \\right)$$ "}, {"identifier": "B", "content": "$$(3, 1)$$ "}, {"identifier": "C", "content": "$$(3,3)$$ "}... | ["C"]
Explanation:
$${\left( {1 + 3{{d\,y} \over {d\,x}}} \right)^2} =$$ (4)<sup>3</sup>$${\left( {{{{d^3}y} \over {d\,{x^3}}}} \right)^3}$$
<br><br>$$ \Rightarrow {\left( {1 + 3{{d\,y} \over {d\,x}}} \right)^2} = 16{\left( {{{{d^3}y} \over {d\,{x^3}}}} \right)^3}$$
<br><br>$$ \therefore $$ Order = 3 and Degree = 3 |
The degree and order of the differential equation of the family of all parabolas whose axis is $$x$$-axis, are respectively.
Options:
[{"identifier": "A", "content": "$$2, 3$$ "}, {"identifier": "B", "content": "$$2,1$$ "}, {"identifier": "C", "content": "$$1,2$$ "}, {"identifier": "D", "content": "$$3,2.$$"}] | ["C"]
Explanation:
General equation of parabola whose axis is along X-axis
<br><br>$${y^2} = 4a\left( {x - h} \right)$$
<br><br>Differentiating with respect to x, we get
<br><br>$$2y{y_1} = 4a$$
<br><br>$$ \Rightarrow y{y_1} = 2a$$
<br><br>Again differentiating with respect to x, we get
<br><br>$$ \Rightarrow {y_1}^2... |
The differential equation representing the family of curves $${y^2} = 2c\left( {x + \sqrt c } \right),$$ where $$c>0,$$ is a parameter, is of order and degree as follows:
Options:
[{"identifier": "A", "content": "order $$1,$$ degree $$2$$"}, {"identifier": "B", "content": "order $$1,$$ degree $$1$$"}, {"identifier... | ["C"]
Explanation:
$${y^2} = 2c\left( {x + \sqrt c } \right)\,\,\,\,\,\,\,\,\,\,...\left( i \right)$$
<br><br>$$2yy' = 2c.1\,\,\,or\,\,\,yy' = c\,\,\,...\left( {ii} \right)$$
<br><br>$$ \Rightarrow {y^2} = 2yy'\left( {x + \sqrt {yy'} } \right)$$
<br><br>$$\left[ \, \right.$$ On putting value of $$c$$ from $$(ii)$$ in ... |
The differential equation whose solution is $$A{x^2} + B{y^2} = 1$$
<br/>where $$A$$ and $$B$$ are arbitrary constants is of
Options:
[{"identifier": "A", "content": "second order and second degree"}, {"identifier": "B", "content": "first order and second degree "}, {"identifier": "C", "content": "first order and f... | ["D"]
Explanation:
$$A{x^2} + B{y^2} = 1\,\,\,\,\,\,\,\,\,\,\,\,\,\,...\left( 1 \right)$$
<br><br>$$Ax + by{{dy} \over {dx}} = 0\,\,\,\,\,\,\,\,\,\,\,\,...\left( 2 \right)$$
<br><br>$$A + By{{{d^2}y} \over {d{x^2}}} + B{\left( {{{dy} \over {dx}}} \right)^2} = 0\,\,\,\,\,\,\,\,\,\,\,\,...\left( 3 \right)$$
<br><br>From... |
The difference between degree and order of a differential equation that represents the family of curves given by $${y^2} = a\left( {x + {{\sqrt a } \over 2}} \right)$$, a > 0 is _________.
Options:
[] | 2
Explanation:
$${y^2} = a\left( {x + {{\sqrt a } \over 2}} \right)$$
<br><br>Differentiating both sides, we get
<br><br>$$2yy' = a$$<br><br>$${y^2} = 2yy'\left( {x + {{\sqrt {2yy'} } \over 2}} \right)$$<br><br>$$y = 2y'\left( {x + {{\sqrt {yy'} } \over {\sqrt 2 }}} \right)$$<br><br>$$y - 2xy' = \sqrt 2 y'\sqrt {yy'} ... |
The solution of the equation $$\,{{{d^2}y} \over {d{x^2}}} = {e^{ - 2x}}$$
Options:
[{"identifier": "A", "content": "$${{{e^{ - 2x}}} \\over 4}$$ "}, {"identifier": "B", "content": "$${{{e^{ - 2x}}} \\over 4} + cx + d$$ "}, {"identifier": "C", "content": "$${1 \\over 4}{e^{ - 2x}} + c{x^2} + d$$ "}, {"identifier": "D... | ["B"]
Explanation:
$${{{a^2}y} \over {d{x^2}}} = {e^{ - 2x}};{\mkern 1mu} $$
<br><br>$${{dy} \over {dx}} = {{{e^{ - 2x}}} \over { - 2}} + c;$$
<br><br>$$y = {{{e^{ - 2x}}} \over 4} + cx + d$$ |
Solution of the differential equation $$ydx + \left( {x + {x^2}y} \right)dy = 0$$ is
Options:
[{"identifier": "A", "content": "$$log$$ $$y=Cx$$"}, {"identifier": "B", "content": "$$ - {1 \\over {xy}} + \\log y = C$$ "}, {"identifier": "C", "content": "$${1 \\over {xy}} + \\log y = C$$ "}, {"identifier": "D", "content... | ["B"]
Explanation:
$$ydx + \left( {x + {x^2}y} \right)dy = 0$$
<br><br>$$ \Rightarrow {{dx} \over {dy}} = - {x \over y} - {x^2}$$
<br><br>$$ \Rightarrow {{dx} \over {dy}} + {x \over y} = - {x^2},$$
<br><br>It is Bernoullis form. Divide by $${x^2}$$
<br><br>$${x^{ - 2}}{{dx} \over {dy}} + {x^{ - 1}}\left( {{1 \over y... |
If $$x{{dy} \over {dx}} = y\left( {\log y - \log x + 1} \right),$$ then the solution of the equation is :
Options:
[{"identifier": "A", "content": "$$y\\log \\left( {{x \\over y}} \\right) = cx$$ "}, {"identifier": "B", "content": "$$x\\log \\left( {{y \\over x}} \\right) = cy$$ "}, {"identifier": "C", "content": "$$\... | ["C"]
Explanation:
$${{xdy} \over {dx}} = y\left( {\log y - \log x + 1} \right)$$
<br><br>$${{dy} \over {dx}} = {y \over x}\left( {\log \left( {{y \over x}} \right) + 1} \right)$$
<br><br>Put $$\,\,\,\,y = vx$$
<br><br>$${{dy} \over {dx}} = v + {{xdv} \over {dx}}$$
<br><br>$$\,\,\,\,\,\,\,\,\,\,\, \Rightarrow v + {{xd... |
Solution of the differential equation
<br/><br>$$\cos x\,dy = y\left( {\sin x - y} \right)dx,\,\,0 < x <{\pi \over 2}$$ is :</br>
Options:
[{"identifier": "A", "content": "$$y\\sec x = \\tan x + c$$ "}, {"identifier": "B", "content": "$$y\\tan x = \\sec x + c$$ "}, {"identifier": "C", "content": "$$\\tan x = \... | ["D"]
Explanation:
$$\cos xdy = y\left( {\sin x - y} \right)dx$$
<br><br>$${{dy} \over {dx}} = y\tan x - {y^2}\,\,\sec \,x$$
<br><br>$${1 \over {{y^2}}}{{dy} \over {dx}} - {1 \over y}\,\tan \,x = - \sec \,x\,....\left( i \right)$$
<br><br>Let $$\,\,\,\,{1 \over y} = t \Rightarrow - {1 \over {{y^2}}}{{dy} \over {dx}}... |
Let $$I$$ be the purchase value of an equipment and $$V(t)$$ be the value after it has been used for $$t$$ years. The value $$V(t)$$ depreciates at a rate given by differential equation $${{dv\left( t \right)} \over {dt}} = - k\left( {T - t} \right),$$ where $$k>0$$ is a constant and $$T$$ is the total life in yea... | ["A"]
Explanation:
$${{dV\left( t \right)} \over {dt}} = - k\left( {T - t} \right)$$
<br><br>$$ \Rightarrow \int {dVt} = - k\int {\left( {T - t} \right)} dt$$
<br><br>$$V\left( t \right) = {{k{{\left( {T - t} \right)}^2}} \over 2} + c$$
<br><br>$$V\left( 0 \right) = I \Rightarrow I = {{K{T^2}} \over 2} + C$$
<br><b... |
The population $$p$$ $$(t)$$ at time $$t$$ of a certain mouse species satisfies the differential equation $${{dp\left( t \right)} \over {dt}} = 0.5\,p\left( t \right) - 450.\,\,$$ If $$p(0)=850,$$ then the time at which the population becomes zero is :
Options:
[{"identifier": "A", "content": "$$2ln$$ $$18$$"}, {"iden... | ["A"]
Explanation:
Given differential equation is
<br><br>$${{dp\left( t \right)} \over {dt}} = 0.5p\left( t \right) - 450$$
<br><br>$$ \Rightarrow {{dp\left( t \right)} \over {dt}} = {1 \over 2}p\left( t \right) - 450$$
<br><br>$$ \Rightarrow {{dp\left( t \right)} \over {dt}} = {{p\left( t \right) - 900} \over 2}$$
... |
At present, a firm is manufacturing $$2000$$ items. It is estimated that the rate of change of production P w.r.t. additional number of workers $$x$$ is given by $${{dp} \over {dx}} = 100 - 12\sqrt x .$$ If the firm employs $$25$$ more workers, then the new level of production of items is
Options:
[{"identifier": "... | ["C"]
Explanation:
Given, Rate of change is $${{dp} \over {dx}} = 100 - 12\sqrt x $$
<br><br>$$ \Rightarrow dP = \left( {100 - 12\sqrt x } \right)dx$$
<br><br>By intergrating $$\int {dP = \int {\left( {100 - 12\sqrt x } \right)} } dx$$
<br><br>$$\int {dP} = \int {\left( {100 - 12\sqrt x } \right)} dx$$
<br><br>$$P = ... |
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