Let $y=y(x)$ be the solution of the differential equation $\left(x^2+4\right)^2 d y+\left(2 x^3 y+8 x…

Let $y=y(x)$ be the solution of the differential equation $\left(x^2+4\right)^2 d y+\left(2 x^3 y+8 x y-2\right) d x=0$. If $y(0)=0$, then $y(2)$ is equal to
  1. $\frac{\pi}{32}$
  2. ${2}{\pi}$
  3. $\frac{\pi}{8}$
  4. $\frac{\pi}{16}$

Solution

$\begin{aligned} & \frac{d y}{d x}+y\left(\frac{2 x^3+8 x}{\left(x^2+4\right)^2}\right)=\frac{2}{\left(x^2+4\right)^2} \\ & \frac{d y}{d x}+y\left(\frac{2 x}{x^2+4}\right)=\frac{2}{\left(x^2+4\right)^2} \\ & \text { IF }=e^{\int \frac{2 x}{x^2+4} d x} \\ & \text { IF }=x^2+4 \\ & y \times\left(x^2+4\right)=\int \frac{2}{\left(x^2+4\right)^2} \times\left(x^2+4\right) \\ & y\left(x^2+4\right)=2 \int \frac{d x}{x^2+2^2} \\ & y\left(x^2+4\right)=\frac{2}{2} \tan ^{-1}\left(\frac{x}{2}\right)+c \\ & 0=0+c=c=0 \\ & y\left(x^2+4\right)=\tan ^{-1}\left(\frac{x}{2}\right) \\ & y \text { at } x=2 \\ & y(4+4)=\tan ^{-1}(1) \\ & y(2)=\frac{\pi}{32} \end{aligned}$

Asked in: JEE Main 2024 (04 Apr Shift 2)

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