Let $y=y(x)$ be the solution curve of the differential equation $x\left(x^2+e^x\right) d y+\left(e^x(x-2)…

Let $y=y(x)$ be the solution curve of the differential equation
$x\left(x^2+e^x\right) d y+\left(e^x(x-2) y-x^3\right) d x=0, x \gt 0$ passing through the point $(1,0)$. Then $y(2)$ is equal to :
  1. $\frac{4}{4-\mathrm{e}^2}$
  2. $\frac{2}{2+\mathrm{e}^2}$
  3. $\frac{2}{2-\mathrm{e}^2}$
  4. $\frac{4}{4+\mathrm{e}^2}$

Solution

$\begin{aligned} & x\left(x^2+e^x\right) d y+\left(e^x(x-2) y-x^3\right) d x=0 \\ & x\left(x^2+e^x\right) \frac{d y}{d x}+e^x(x-2) y=x^3 \\ & \frac{d y}{d x}+\frac{e^x(x-2)}{x\left(x^2+e^x\right)} y=\frac{x^2}{x^2+e^x} \\ & \text { I.F. }=e^{\int \frac{e^x(x-2)}{x\left(x^2+e^x\right)} d x}=e^{\int \frac{e^x\left(\frac{1}{x^2}-\frac{2}{x^2}\right) d x}{\left(1+\frac{e^x}{x^2}\right)} d x}\end{aligned}$
Let $1+\frac{e^x}{x^2}=t \Rightarrow \frac{x^2 e^x-e^x 2 x}{x^4} d x=d t$
$\Rightarrow \text { I.F. } \mathrm{e}^{\ln \left(1+\frac{\mathrm{e}^2}{\mathrm{x}^2}\right)}=1+\frac{\mathrm{e}^{\mathrm{x}}}{\mathrm{x}^2}$
Now $y\left(1+\frac{e^x}{x^2}\right)=\int \frac{x^2}{x^2+e^x} \cdot \frac{x^2+e^x}{x^2} d x+C$
$y\left(1+\frac{e^x}{x^2}\right)=x+C$
Passing through $(1,0)$
$\begin{aligned}
& \Rightarrow C=-1 \\ & y=\frac{x-1}{1+\frac{e^x}{x^2}} \\ & y(2)=\frac{1}{1+\frac{e^2}{4}}=\frac{4}{4+e^2}
\end{aligned}$

Asked in: JEE Main 2025 (07 Apr Shift 1)

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