Differential equations find their applications in the explanation of many real-life phenomena involving temporal change of quantities. For instance, city population growth typically exhibits a model with the growth rate proportional to the current population; this process can be explained using a straightforward exponential differential equation. In the same way, a balloon inflation with gas filled depends on pressures and temperatures, and the process can be explained with differential equations formulated from gas laws.
Created according to the latest CBSE 2025-26 syllabus, the NCERT Solutions for Class 12 Maths Chapter 9 Miscellaneous Exercise are created by subject experts at Careers360. The solutions give detailed, step-by-step solutions to help students better understand even complicated problems.
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Question 1: Indicate Order and Degree.
(i) $\frac{d^2y}{dx^2} + 5x \left (\frac{dy}{dx} \right )^2-6y = \log x$
Answer:
Given function is
$\frac{d^2y}{dx^2} + 5x \left (\frac{dy}{dx} \right )^2-6y = \log x$
We can rewrite it as
$y''+5x(y')^2-6y = \log x$
Now, it is clear from the above that, the highest order derivative present in differential equation is $y''$
Therefore, the order of the given differential equation $\frac{d^2y}{dx^2} + 5x \left (\frac{dy}{dx} \right )^2-6y = \log x$ is 2
Now, the given differential equation is a polynomial equation in its derivative y '' and y 'and power raised to y '' is 1
Therefore, it's degree is 1
Question 1: Indicate Order and Degree.
(ii) $\left(\frac{dy}{dx} \right )^3 - 4\left(\frac{dy}{dx} \right )^2 + 7y = \sin x$
Answer:
Given function is
$\left(\frac{dy}{dx} \right )^3 - 4\left(\frac{dy}{dx} \right )^2 + 7y = \sin x$
We can rewrite it as
$(y')^3-4(y')^2+7y=\sin x$
Now, it is clear from the above that, the highest order derivative present in differential equation is y'
Therefore, order of given differential equation is 1
Now, the given differential equation is a polynomial equation in it's dervatives y 'and power raised to y ' is 3
Therefore, it's degree is 3
Question 1: Indicate Order and Degree.
(iii) $\frac{d^4 y}{dx^4} - \sin\left(\frac{d^3y}{dx^3} \right ) = 0$
Answer:
Given function is
$\frac{d^4 y}{dx^4} - \sin\left(\frac{d^3y}{dx^3} \right ) = 0$
We can rewrite it as
$y''''-\sin y''' = 0$
Now, it is clear from the above that, the highest order derivative present in differential equation is y''''
Therefore, order of given differential equation is 4
Now, the given differential equation is not a polynomial equation in it's dervatives
Therefore, it's degree is not defined
(i) $xy = ae^x + be^{-x} + x^2\qquad :\ x\frac{d^2y}{dx^2} + 2\frac{dy}{dx} - xy +x^2 -2 =0$
Answer:
Given,
$xy = ae^x + be^{-x} + x^2$
Now, differentiating both sides w.r.t. x,
$x\frac{dy}{dx} + y = ae^x - be^{-x} + 2x$
Again, differentiating both sides w.r.t. x,
$\\ (x\frac{d^2y}{dx^2} + \frac{dy}{dx}) + \frac{dy}{dx} = ae^x + be^{-x} + 2 \\ $
$\implies x\frac{d^2y}{dx^2} + 2\frac{dy}{dx} = ae^x + be^{-x} + 2 \\ $
$\implies x\frac{d^2y}{dx^2} + 2\frac{dy}{dx} = xy -x^2 + 2 \\$
$\implies x\frac{d^2y}{dx^2} + 2\frac{dy}{dx} - xy + x^2 + 2$
Therefore, the given function is the solution of the corresponding differential equation.
(ii) $y = e^x(a\cos x + b \sin x )\qquad : \ \frac{d^2y}{dx^2} - 2\frac{dy}{dx} + 2y = 0$
Answer:
Given,
$y = e^x(a\cos x + b \sin x )$
Now, differentiating both sides w.r.t. x,
$\frac{dy}{dx} = e^x(-a\sin x + b \cos x ) + e^x(a\cos x + b \sin x ) =e^x(-a\sin x + b \cos x ) +y$
Again, differentiating both sides w.r.t. x,
$\\ \frac{d^2y}{dx^2} = e^x(-a\cos x - b \sin x ) + e^x(-a\sin x + b \cos x ) + \frac{dy}{dx} \\$
$= -y + (\frac{dy}{dx} -y) + \frac{dy}{dx} \\$
$\implies \frac{d^2y}{dx^2} - 2\frac{dy}{dx} + 2y = 0$
Therefore, the given function is the solution of the corresponding differential equation.
(iii) $y= x\sin 3x \qquad : \ \frac{d^2y}{dx^2} + 9y - 6\cos 3x = 0$
Answer:
Given,
$y= x\sin 3x$
Now, differentiating both sides w.r.t. x,
$y= x\sin 3x \frac{dy}{dx} = x(3\cos 3x) + \sin 3x$
Again, differentiating both sides w.r.t. x,
$\\ \frac{d^2y}{dx^2} = 3x(-3\sin 3x) + 3\cos 3x + 3\cos 3x \\ $
$= -9y + 6\cos 3x \\$
$\implies \frac{d^2y}{dx^2} + 9y - 6\cos 3x = 0$
Therefore, the given function is the solution of the corresponding differential equation.
(iv) $x^2 = 2y^2\log y\qquad : \ (x^2 + y^2)\frac{dy}{dx} - xy = 0$
Answer:
Given,
$x^2 = 2y^2\log y$
Now, differentiating both sides w.r.t. x,
$\\ 2x = (2y^2.\frac{1}{y} + 2(2y)\log y)\frac{dy}{dx} = 2(y + 2y\log y)\frac{dy}{dx} \\$
$\implies \frac{dy}{dx} = \frac{x}{y(1+ 2\log y)}$
Putting $\frac{dy}{dx}\ and \ x^2$ values in LHS
$\\ (2y^2\log y + y^2)\frac{dy}{dx} - xy = y^2(2\log y + 1)\frac{x}{y(1+ 2\log y)} -xy \\$
$= xy - xy = 0 = RHS$
Therefore, the given function is the solution of the corresponding differential equation.
Answer:
Given equation is
$(x-a)^2 + 2y^2 = a^2$
we can rewrite it as
$2y^2 = a^2-(x-a)^2$ -(i)
Differentiate both the sides w.r.t x
$\frac{d\left ( 2y^2 \right )}{dx}=\frac{d(a^2-(x-a)^2)}{dx}$
$4yy^{'}=4y\frac{dy}{dx}=-2(x-a)\\ \\$
$(x-a)= -2yy'\Rightarrow a = x+2yy'$ -(ii)
Put value from equation (ii) in (i)
$(-2yy')^2+2y^2= (x+2yy')^2\\$
$4y^2(y')^2+2y^2= x^2+4y^2(y')^2+4xyy'\\$
y' = \frac{2y^2-x^2}{4xy}$
Therefore, the required differential equation is $y' = \frac{2y^2-x^2}{4xy}$
Answer:
Given,
$
\begin{aligned}
& \left(x^3-3 x y^2\right) d x=\left(y^3-3 x^2 y\right) d y \\
& \Longrightarrow \frac{d y}{d x}=\frac{\left(x^3-3 x y^2\right)}{\left(y^3-3 x^2 y\right)}
\end{aligned}
$
Now, let $\mathbf{y}=\mathrm{vx}$
$
\Longrightarrow \frac{d y}{d x}=\frac{d(v x)}{d x}=v+x \frac{d v}{d x}
$
Substituting the values of $y$ and $y^{\prime}$ in the equation,
$
\begin{aligned}
& v+x \frac{d v}{d x}=\frac{\left(x^3-3 x(v x)^2\right)}{\left((v x)^3-3 x^2(v x)\right)} \\
& \Longrightarrow v+x \frac{d v}{d x}=\frac{1-3 v^2}{v^3-3 v} \\
& \Longrightarrow x \frac{d v}{d x}=\frac{1-3 v^2}{v^3-3 v}-v=\frac{1-v^4}{v^3-3 v} \\
& \Longrightarrow\left(\frac{v^3-3 v}{1-v^4}\right) d v=\frac{d x}{x}
\end{aligned}
$
Integrating both sides we get,
$
\int\left(\frac{v^3-3 v}{1-3 v^4}\right) d v=\log x+\log C^{\prime}
$
Now, $\int\left(\frac{v^3-3 v}{1-3 v^4}\right) d v=\int \frac{v^3}{1-v^4} d v-3 \int \frac{v d v}{1-v^4}$
$
\Rightarrow \int\left(\frac{v^3-3 v}{1-3 v^4}\right) d v=I_1-3 I_2 \text {, where } I_1=\int \frac{v^3}{1-v^4} d v \text { and } I_2=\int \frac{v d v}{1-v^4}
$
Let $1-v^4=\mathrm{t}$
$
\begin{aligned}
& \frac{d}{d v}\left(1-v^4\right)=\frac{d t}{d v} \\
& \Longrightarrow-4 v^3=\frac{d t}{d v} \\
& \Longrightarrow v^3 d v=-\frac{d t}{4}
\end{aligned}
$
Now,
$
\mathrm{I}_1=\int-\frac{\mathrm{dt}}{4}=-\frac{1}{4} \log \mathrm{t}=-\frac{1}{4} \log \left(1-\mathrm{v}^4\right)
$
and
$
I_2=\int \frac{v d v}{1-v^4}=\int \frac{v d v}{1-\left(v^2\right)^2}
$
Let $v^2=p$
$
\begin{aligned}
& \Rightarrow \frac{d}{d v}\left(v^2\right)=\frac{d p}{d v} \\
& \Rightarrow 2 v=\frac{d p}{d v}
\end{aligned}
$
$
\Rightarrow \mathrm{vdv}=\frac{\mathrm{dp}}{2}
$
$
\therefore \mathrm{I}_2=\frac{1}{2} \int \frac{\mathrm{dp}}{1-\mathrm{p}^2}=\frac{1}{2 \times 2} \log \left|\frac{1+\mathrm{p}}{1-\mathrm{p}}\right|=\frac{1}{4}\left|\frac{1+\mathrm{v}^2}{1-\mathrm{v}}\right|
$
Now, substituting the values of $\mathrm{I}_1$ and $\mathrm{I}_2$ in the above equation, we get,
$
\int\left(\frac{\mathrm{v}^3-3 \mathrm{y}}{1-\mathrm{v}^4}\right) \mathrm{dv}=-\frac{1}{4} \log \left(1-\mathrm{v}^4\right)-\frac{3}{4} \log \left|\frac{1+\mathrm{v}^2}{1-\mathrm{v}^2}\right|
$
Thus,
$
\begin{aligned}
& -\frac{1}{4} \log \left(1-\mathrm{v}^4\right)-\frac{3}{4} \log \left|\frac{1+\mathrm{v}^2}{1-\mathrm{v}^2}\right|=\log \mathrm{x}+\log \mathrm{C}^{\prime} \\
& \Rightarrow-\frac{1}{4} \log \left[\left(1-\mathrm{v}^4\right)\left(\frac{1+\mathrm{v}^2}{1-\mathrm{v}^2}\right)^3\right]=\log \mathrm{C}^{\prime} \mathrm{x} \\
& \Rightarrow \frac{\left(1+\mathrm{v}^2\right)^4}{\left(1-\mathrm{v}^2\right)^2}=\left(\mathrm{C}^{\prime} \mathrm{x}\right)^{-4} \\
& \Rightarrow \frac{\left(1+\frac{y^2}{x^2}\right)^4}{\left(1-\frac{y^2}{x^2}\right)^2}=\frac{1}{\mathrm{C}^4 \mathrm{x}^4} \\
& \left(x^2-y^2\right)^2=C^{\prime 4}\left(x^2+y^2\right)^4 \\
& \Longrightarrow\left(x^2-y^2\right)=C^{\prime 2}\left(x^2+y^2\right)^2 \\
& \Longrightarrow\left(x^2-y^2\right)=K\left(x^2+y^2\right)^2, \text { where } K=C^{\prime 2}
\end{aligned}
$
Answer:
Now, equation of the circle with center at (x,y) and radius r is
$(x-a)^2+(y-b)^2 = r^2$
Since, it touch the coordinate axes in first quadrant
Therefore, x = y = r
$(x-a)^2+(y-a)^2 = a^2$ -(i)
Differentiate it w.r.t x
we will get
$2(x-a)+2(y-a)y'= 0\\ $
$\\ 2x-2a+2yy'-2ay' = 0\\$
$a=\frac{x+yy'}{1+y'}$ -(ii)
Put value from equation (ii) in equation (i)
$(x-\frac{x+yy'}{1+y'})^2+(y-\frac{x+yy'}{1+y'})^2=\left ( \frac{x+yy'}{1+y'} \right )^2\\$
$\\ (x+xy'-x-yy')^2+(y+yy'-x-yy')^2=(x+yy')^2\\ $
$\\ (y')^2(x-y)^2+(x-y)^2=(x+yy')^2\\$
$\\ (x-y)^2\left ( (y')^2+1 \right )=(x+yy')^2$
Therefore, the differential equation of the family of circles in the first quadrant which touches the coordinate axes is $(x-y)^2\left ( (y')^2+1 \right )=(x+yy')^2$
Question 6: Find the general solution of the differential equation $\frac{dy}{dx} + \sqrt{\frac{1 - y^2}{1-x^2}} = 0$
Answer:
Given equation is
$\frac{dy}{dx} + \sqrt{\frac{1 - y^2}{1-x^2}} = 0$
we can rewrite it as
$\frac{dy}{dx } =- \sqrt{\frac{1-y^2}{1-x^2}}\\$
$\\ \frac{dy}{\sqrt{1-y^2}}= \frac{-dx}{\sqrt{1-x^2}}$
Now, integrate on both the sides
$\sin^{-1}y + C =- \sin ^{-1}x + C'\\ $
$\\ \sin^{-1}y+\sin^{-1}x= C$
Therefore, the general solution of the differential equation $\frac{dy}{dx} + \sqrt{\frac{1 - y^2}{1-x^2}} = 0$ is $\sin^{-1}y+\sin^{-1}x= C$
Answer:
Given,
$
\begin{aligned}
& \frac{d y}{d x}+\frac{y^2+y+1}{x^2+x+1}=0 \\
& \Rightarrow \frac{\mathrm{dy}}{\mathrm{dx}}=-\left(\frac{\mathrm{y}^2+\mathrm{y}+1}{\mathrm{x}^2+\mathrm{x}+1}\right) \\
& \Rightarrow \frac{\mathrm{dy}}{\mathrm{y}^2+\mathrm{y}+1}=\frac{-\mathrm{dx}}{\mathrm{x}^2 \mathrm{dx}+1} \\
& \Rightarrow \frac{\mathrm{dy}}{\mathrm{y}^2+\mathrm{y}+1}+\frac{\mathrm{dx}}{\mathrm{x}^2+\mathrm{x}+1}=0
\end{aligned}
$
Integrating both sides,
$
\begin{aligned}
& \int \frac{d y}{y^2+y+1}+\int \frac{d x}{x^2+x+1}=C \\
& \Rightarrow \int \frac{d y}{\left(y+\frac{1}{2}\right)^2+\left(\frac{\sqrt{3}}{2}\right)^2}+\int \frac{d y}{\left(x+\frac{1}{2}\right)^2+\left(\frac{\sqrt{3}}{2}\right)^2}=C \\
& \Rightarrow \frac{2}{\sqrt{3}} \tan ^{-1}\left[\frac{\mathrm{y}+\frac{1}{2}}{\frac{\sqrt{3}}{2}}\right]+\frac{2}{\sqrt{3}} \tan ^{-1}\left[\frac{x+\frac{1}{2}}{\frac{\sqrt{3}}{2}}\right]=C \\
& \Rightarrow \tan ^{-1}\left[\frac{2 y+1}{\sqrt{3}}\right]+\tan ^{-1}\left[\frac{2 x+1}{\sqrt{3}}\right]=\mathrm{C} \Rightarrow \tan ^{-1}\left[\frac{\frac{2 y+1}{\sqrt{3}}+\frac{2 x+1}{\sqrt{3}}}{1-\frac{2 y+1}{\sqrt{3}} \cdot \frac{2 x+1}{\sqrt{3}}}\right]=\frac{\sqrt{3}}{2} C \\
& \Rightarrow \tan ^{-1}\left[\frac{\frac{2 x+2 y+2}{\sqrt[3]{3}}}{1-\left(\frac{4 x y+2 x+2 y+1}{3}\right)}\right]=\frac{\sqrt{3}}{2} C \\
& \Rightarrow \tan ^{-1}\left[\frac{2 \sqrt{3}(x+y+1)}{3-4 x y-2 x-2 y-1}\right]=\frac{\sqrt{3}}{2} C \\
& \Rightarrow \tan ^{-1}\left[\frac{2 \sqrt{3}(x+y+1)}{2(1-x-y-2 x y)}\right]=\frac{\sqrt{3}}{2} C \\
& \Rightarrow \frac{\sqrt{3}(x+y+1)}{(1-x-y-2 x y)}=\tan \left(\frac{\sqrt{3}}{2} c\right)
\end{aligned}
$
Let $\tan \left(\frac{\sqrt{3}}{2} c\right)=B$
$
x+y+1=\frac{2 B}{\sqrt{3}}(1-x-y-2 x y)
$
Let $A=\frac{2 B}{\sqrt{3}}$,
$
x+y+1=A(1-x-y-2 x y)
$
Hence proved.
Answer:
Given equation is
$\sin x \cos y dx + \cos x \sin y dy = 0.$
we can rewrite it as
$\frac{dy}{dx}= -\tan x\cot y\\$
$\\ \frac{dy}{\cot y}= -\tan xdx\\$
$\\ \tan y dy =- \tan x dx$
Integrate both the sides
$\log |\sec y|+C' = -\log|sec x|- C''\\ $
$\\ \log|\sec y | +\log|\sec x| = C\\$
$\\ \sec y .\sec x = e^{C}$
Now by using boundary conditiond, we will find the value of C
It is given that the curve passing through the point $\left(0,\frac{\pi}{4} \right )$
So,
$\sec \frac{\pi}{4} .\sec 0 = e^{C}\\ $
$\\ \sqrt2.1= e^C\\$
$\\ C = \log \sqrt2$
Now,
$\sec y.\sec x= e^{\log \sqrt 2}\\$
$\\ \frac{\sec x}{\cos y} = \sqrt 2\\ $
$\\ \cos y = \frac{\sec x}{\sqrt 2}$
Therefore, the equation of the curve passing through the point $\left(0,\frac{\pi}{4} \right )$ whose differential equation is $\sin x \cos y dx + \cos x \sin y dy = 0.$ is $\cos y = \frac{\sec x}{\sqrt 2}$
Answer:
Given equation is
$(1 + e^ {2x} ) dy + (1 + y^2 ) e^x dx = 0$
we can rewrite it as
$\frac{dy}{dx}= -\frac{(1+y^2)e^x}{(1+e^{2x})}\\ $
$\\ \frac{dy}{1+y^2}= \frac{-e^xdx}{1+e^{2x}}$
Now, integrate both the sides
$\tan^{-1}y + C' =\int \frac{-e^{x}dx}{1+e^{2x}}$
$\int \frac{-e^{x}dx}{1+e^{2x}}\\$
Put
$e^x = t \\$
$e^xdx = dt$
$\int \frac{dt}{1+t^2}= \tan^{-1}t + C''$
Put $t = e^x$ again
$\int \frac{-e^{x}dx}{1+e^{2x}} = -\tan ^{-1}e^x+C''$
Put this in our equation
$\tan^{-1}y = -\tan ^{-1}e^x+C\\$
$\tan^{-1}y +\tan ^{-1}e^x=C$
Now, by using boundary conditions we will find the value of C
It is given that
y = 1 when x = 0
$\\ \tan^{-1}1 +\tan ^{-1}e^0=C\\ $
$\\ \frac{\pi}{4}+\frac{\pi}{4}= C\\$
$C = \frac{\pi}{2}$
Now, put the value of C
$\tan^{-1}y +\tan ^{-1}e^x=\frac{\pi}{2}$
Therefore, the particular solution of the differential equation $(1 + e^ {2x} ) dy + (1 + y^2 ) e^x dx = 0$ is $\tan^{-1}y +\tan ^{-1}e^x=\frac{\pi}{2}$
Answer:
Given,
$ye^\frac{x}{y}dx = (xe^\frac{x}{y} + y^2)dy$
$\\ ye^\frac{x}{y}\frac{dx}{dy} = xe^\frac{x}{y} + y^2 \\$
$\implies e^\frac{x}{y}[y\frac{dx}{dy} -x] = y^2 \\$
$\implies \frac{e^\frac{x}{y}[y\frac{dx}{dy} -x]}{y^2} = 1$
Let $\large e^\frac{x}{y} = t$
Differentiating it w.r.t. y, we get,
$\\ \frac{d}{dy}e^\frac{x}{y} = \frac{dt}{dy} \\$
$ \implies e^\frac{x}{y}.\frac{d}{dy}(\frac{x}{y}) = \frac{dt}{dy} \\$
$\implies \frac{e^\frac{x}{y}[y\frac{dx}{dy} -x]}{y^2} =\frac{dt}{dy}$
Thus from these two equations,we get,
$\\ \frac{dt}{dy} = 1 \\ $
$\implies \int dt = \int dy \\ $
$\implies t = y + C$
$\Longrightarrow e^{\frac{x}{y}}=y+C$
Answer:
Given equation is
$(x - y) (dx + dy) = dx - dy,$
Now, integrate both the sides
Put
$(x-y ) = t\\ $
$dx - dy = dt$
Now, given equation become
$dx+dy= \frac{dt}{t}$
Now, integrate both the sides
$x+ y + C '= \log t + C''$
Put $t = x- y$ again
$x+y = \log (x-y)+ C$
Now, by using boundary conditions we will find the value of C
It is given that
y = -1 when x = 0
$0+(-1) = \log (0-(-1))+ C\\$
$C = -1$
Now, put the value of C
$x+y = \log |x-y|-1\\ $
$\log|x-y|= x+y+1$
Therefore, the particular solution of the differential equation $(x - y) (dx + dy) = dx - dy,$ is $\log|x-y|= x+y+1$
Answer:
Given,
$
\begin{aligned}
& {\left[\frac{e^{-2 \sqrt{x}}}{\sqrt{x}}-\frac{y}{\sqrt{x}}\right] \frac{d x}{d y}=1} \\
& \Rightarrow \frac{\mathrm{dy}}{\mathrm{dx}}=\frac{\mathrm{e}^{-2 \sqrt{x}}}{\sqrt{\mathrm{x}}}-\frac{\mathrm{y}}{\sqrt{x}} \\
& \Longrightarrow \frac{\mathrm{dy}}{\mathrm{dx}}+\frac{\mathrm{y}}{\sqrt{\mathrm{x}}}=\frac{\mathrm{e}^{-2 \sqrt{x}}}{\sqrt{\mathrm{x}}}
\end{aligned}
$
This is equation is in the form of $\frac{d y}{d x}+p y=Q$
$
p=\frac{1}{\sqrt{x}} \text { and } Q=\frac{e^{-2 \sqrt{x}}}{\sqrt{x}}
$
Now, I.F. $=\mathrm{e}^{\int \mathrm{pdx}}=\mathrm{e}^{\int \frac{1}{\sqrt{x}} \mathrm{dx}}=\mathrm{e}^{2 \sqrt{\mathrm{x}}}$
We know that the solution of the given differential equation is:
$
\begin{aligned}
& y(I \cdot F \cdot)=\int(Q \cdot F \cdot) d x+C \\
& \Rightarrow \mathrm{ye}^{2 \sqrt{\mathrm{x}}}=\int\left(\frac{\mathrm{e}^{-2 \sqrt{x}}}{\sqrt{\mathrm{x}}} \times \mathrm{e}^{2 \sqrt{\mathrm{x}}}\right) \mathrm{dx}+C \\
& \Rightarrow \mathrm{ye}^{2 \sqrt{\mathrm{x}}}=\int \frac{1}{\sqrt{\mathrm{x}}} \mathrm{dx}+\mathrm{C} \\
& \Rightarrow \mathrm{ye}^{2 \sqrt{x}}=2 \sqrt{\mathrm{x}}+C
\end{aligned}
$
Answer:
Given equation is
$\frac{dy}{dx} + y \cot x = 4x \textup{cosec} x\ (x\neq 0)$
This is $\frac{dy}{dx} + py = Q$ type where $p =\cot x$ and $Q = 4xcosec x$ $Q = 4x \ cosec x$
Now,
$I.F. = e^{\int pdx}= e^{\int \cot xdx}= e^{\log |\sin x|}= \sin x$
Now, the solution of given differential equation is given by relation
$y(I.F.) =\int (Q\times I.F.)dx +C$
$y(\sin x ) =\int (\sin x\times 4x \ cosec x)dx +C$
$y(\sin x) =\int(\sin x\times \frac{4x}{\sin x}) +C\\$
$\\ y(\sin x) = \int 4x + C\\ $
$y\sin x= 2x^2+C$
Now, by using boundary conditions we will find the value of C
It is given that y = 0 when $x= \frac{\pi}{2}$
at $x= \frac{\pi}{2}$
$0.\sin \frac{\pi}{2 } = 2.\left ( \frac{\pi}{2} \right )^2+C\\$
$\\ C = - \frac{\pi^2}{2}$
Now, put the value of C
$y\sin x= 2x^2-\frac{\pi^2}{2}$
Therefore, the particular solution is $y\sin x= 2x^2-\frac{\pi^2}{2}, (sinx\neq0)$
Answer:
Given equation is
$(x+1)\frac{dy}{dx} = 2e^{-y} -1$
we can rewrite it as
$\frac{e^ydy}{2-e^y}= \frac{dx}{x+1}\\$
Integrate both the sides
$\int \frac{e^ydy}{2-e^y}= \log |x+1|\\$
$\int \frac{e^ydy}{2-e^y}$
Put
$2-e^y = t\\$
$-e^y dy = dt$
$\int \frac{-dt}{t}=- \log |t|$
put $t = 2- e^y$ again
$\int \frac{e^ydy}{2-e^y} =- \log |2-e^y|$
Put this in our equation
$\log |2-e^y| + C'= \log|1+x| + C''\\$
$\log (2-e^y)^{-1}= \log (1+x)+\log C\\$
$\frac{1}{2-e^y}= C(1+x)$
Now, by using boundary conditions we will find the value of C
It is given that y = 0 when x = 0
at x = 0
$\frac{1}{2-e^0}= C(1+0)\\ C = \frac{1}{2}$
Now, put the value of C
$\frac{1}{2-e^y} = \frac{1}{2}(1+x)\\ $'
$\\ \frac{2}{1+x}= 2-e^y\\$
$\frac{2}{1+x}-2= -e^y\\$
$-\frac{2x-1}{1+x} = -e^y\\$
$y = \log \frac{2x-1}{1+x}$
Therefore, the particular solution is $y = \log \frac{2x-1}{1+x}, x\neq-1$
Answer:
Let n be the population of the village at any time t.
According to question,
$\frac{dn}{dt} = kn\ \ (k\ is\ a\ constant)$
$\\ \implies \int \frac{dn}{n} = \int kdt \\$
$\implies \log n = kt + C$
Now, at t=0, n = 20000 (Year 1999)
$\\ \implies \log (20000) = k(0) + C \\$
$\implies C = \log2 + 4$
Again, at t=5, n= 25000 (Year 2004)
$\\ \implies \log (25000) = k(5) + \log2 + 4 \\$
$\implies \log 25 + 3 = 5k + \log2 +4 \\$
$\implies 5k = \log 25 - \log2 -1 =\log \frac{25}{20} \\$
$\implies k = \frac{1}{5}\log \frac{5}{4}$
Using these values, at t =10 (Year 2009)
$\\ \implies \log n = k(10)+ C \\$
$\implies \log n = \frac{1}{5}\log \frac{5}{4}(10) + \log2 + 4 \\$
$\implies \log n = \log(\frac{25.2.10000}{16}) = \log(31250) \\$
$\therefore n = 31250$
Therefore, the population of the village in 2009 will be 31250.
Question 16: The general solution of the differential equation $\frac{ydx - xdy}{y} = 0$ is
(A) $xy = C$
(B) $x = Cy^2$
(C) $y = Cx$
(D) $y = Cx^2$
Answer:
Given equation is
$\frac{ydx - xdy}{y} = 0$
we can rewrite it as
$dx = \frac{x}{y}dy\\$
$\frac{dy}{y}=\frac{dx}{x}$
Integrate both the sides
we will get
$\log |y| = \log |x| + C\\ $
\log \frac{y}{x} = C \\ $
$\frac{y}{x} = e^C\\$
$\frac{y}{x} = C\\$
$y = Cx$
Therefore, answer is (C)
Question 17: The general solution of a differential equation of the type $\frac{dx}{dy} + P_1 x = Q_1$ is
(A) $ye^{\int P_1 dy} = \int \left(Q_1 e^{\int P_1 dy} \right )dy +C$
(B) $ye^{\int P_1 dx} = \int \left(Q_1 e^{\int P_1 dx} \right )dx +C$
(C) $xe^{\int P_1 dy} = \int \left(Q_1 e^{\int P_1 dy} \right )dy +C$
(D) $xe^{\int P_1 dx} = \int \left(Q_1 e^{\int P_1 dx} \right )dx +C$
Answer:
Given equation is
$\frac{dx}{dy} + P_1 x = Q_1$
and we know that the general equation of such type of differential equation is
$xe^{\int p_1dy} = \int (Q_1e^{\int p_1dy})dy+ C$
Therefore, the correct answer is (C)
Question 18: The general solution of the differential equation $e^x dy + (y e^x + 2x) dx = 0$ is
(A) $xe^y + x^2 = C$
(B) $xe^y + y^2 = C$
(C) $ye^x + x^2 = C$
(D) $ye^y + x^2 = C$
Answer:
Given equation is
$e^x dy + (y e^x + 2x) dx = 0$
we can rewrite it as
$\frac{dy}{dx}+y=-2xe^{-x}$
It is $\frac{dy}{dx}+py=Q$ type of equation where $p = 1 \ and \ Q = -2xe^{-x}$
Now,
$I.F. = e^{\int p dx }= e^{\int 1dx}= e^x$
Now, the general solution is
$y(I.F.) = \int (Q\times I.F.)dx+C$
$y(e^x) = \int (-2xe^{-x}\times e^x)dx+C\\$
$ye^x= \int -2xdx + C\\$
$ye^x=- x^2 + C\\ $
$ye^x+x^2 = C$
Therefore, (C) is the correct answer
Also check-
Topics | Description | Example |
Variable Separable Method | Used when the equation can be rearranged to separate variables x and y on opposite sides. | $\begin{aligned} & \text { Solve: } \frac{d y}{d x}=x\left(1+y^2\right) \\ & \Rightarrow \frac{1}{1+y^2} d y=x d x \\ & \Rightarrow \tan ^{-1} y=\frac{x^2}{2}+C\end{aligned}$ |
Homogeneous Differential Equations | Equations where both numerator and denominator are homogeneous functions of the same degree. Substitution y=vx is used. | Solve: $\frac{d y}{d x}=\frac{x+y}{x}$ Let $y=v x$, then reduce and solve. |
Linear Differential Equations | First-order equations of the form \frac{d y}{d x}+P(x) y=Q(x). Solved using integrating factor (IF). | Solve: $\frac{d y}{d x}+y=e^x$ IF $=e^{\int 1 d x}=e^x$, then multiply and integrate. |
Exact Differential Equations | When a DE is of the form $M(x, y) d x+N(x, y) d y=0$ and satisfies $\frac{\partial M}{\partial y}=\frac{\partial N}{\partial x}$. | Solve: $\left(2 x y+y^2\right) d x+\left(x^2+2 x y\right) d y=0$ Check for exactness and integrate accordingly. |
Word Problems/Applications | Real-life problems involving growth, decay, cooling, etc., modeled and solved using DEs. | A population grows at a rate proportional to its size. If it doubles in 3 years, find it after 5 years. |
Solving Using Initial Conditions | After solving, use a given point (like y(x0)=y0) to find the constant of integration C. | General: $y=C e^x$, given $y(0)=2 \Rightarrow 2=C \Rightarrow$ Particular $y=2 e^x$ |
Order and Degree of a Differential Equation | Identifying the order (highest derivative) and degree (power of highest derivative when equation is polynomial in derivatives). | \text { For }\left(\frac{d^2 y}{d x^2}\right)^3+y=0 \text { : Order }=2 \text {, Degree }=3 |
Also Read-
Frequently Asked Questions (FAQs)
The first exercise covers the topic order and degree of differential equations
Solutions to linear differential equations
After completing the chapter students can test their knowledge through miscellaneous exercises since it covers questions from all main topics of the chapter.
Seven including the miscellaneous exercise.
18 questions are covered in the miscellaneous exercise of chapter 9 Class 12 NCERT book
3 multiple choice questions with 4 options for each are covered in the Class 12 Maths chapter 9 miscellaneous exercise .
The main topics covered in the chapter are order and degree, general and peculiar solutions of differential equations, formation of the differential equation for which general solution is given and a few methods to solve differential equations.
On Question asked by student community
Hello,
The date of 12 exam is depends on which board you belongs to . You should check the exact date of your exam by visiting the official website of your respective board.
Hope this information is useful to you.
Hello,
Class 12 biology questions papers 2023-2025 are available on cbseacademic.nic.in , and other educational website. You can download PDFs of questions papers with solution for practice. For state boards, visit the official board site or trusted education portal.
Hope this information is useful to you.
Hello Pruthvi,
Taking a drop year to reappear for the Karnataka Common Entrance Test (KCET) is a well-defined process. As a repeater, you are fully eligible to take the exam again to improve your score and secure a better rank for admissions.
The main procedure involves submitting a new application for the KCET through the official Karnataka Examinations Authority (KEA) website when registrations open for the next academic session. You must pay the required application fee and complete all formalities just like any other candidate. A significant advantage for you is that you do not need to retake your 12th board exams. Your previously secured board marks in the qualifying subjects will be used again. Your new KCET rank will be calculated by combining these existing board marks with your new score from the KCET exam. Therefore, your entire focus during this year should be on preparing thoroughly for the KCET to achieve a higher score.
For more details about the KCET Exam preparation,
CLICK HERE.
I hope this answer helps you. If you have more queries, feel free to share your questions with us, and we will be happy to assist you.
Thank you, and I wish you all the best in your bright future.
Yes, you can switch from Science in Karnataka State Board to Commerce in CBSE for 12th. You will need a Transfer Certificate from your current school and meet the CBSE school’s admission requirements. Since you haven’t studied Commerce subjects like Accountancy, Economics, and Business Studies, you may need to catch up before or during 12th. Not all CBSE schools accept direct admission to 12th from another board, so some may ask you to join Class 11 first. Make sure to check the school’s rules and plan your subject preparation.
Hello
For the 12th CBSE Hindi Medium board exam, important questions usually come from core chapters like “Madhushala”, “Jhansi ki Rani”, and “Bharat ki Khoj”.
Questions often include essay writing, letter writing, and comprehension passages. Grammar topics like Tenses, Voice Change, and Direct-Indirect Speech are frequently asked.
Students should practice poetry questions on themes and meanings. Important questions also cover summary writing and translation from Hindi to English or vice versa.
Previous years’ question papers help identify commonly asked questions.
Focus on writing practice to improve handwriting and presentation. Time management during exams is key to answering all questions effectively.
This ebook serves as a valuable study guide for NEET 2025 exam.
This e-book offers NEET PYQ and serves as an indispensable NEET study material.
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