The general solution of the differential equation $\left(x^2+2\right)$ $d y+2 x y d x=e^x\left(x^2+2\right)…

The general solution of the differential equation $\left(x^2+2\right)$ $d y+2 x y d x=e^x\left(x^2+2\right) d x$ is
  1. $\frac{x}{y}=e^x\left(x^2+x-4\right)+c$
  2. $2 x y=e^x\left(x^2-2 x+4\right)+c$
  3. $\left(x^2+2\right) y=e^x\left(x^2-2 x+4\right)+c$
  4. $\left(x^2+2\right)^2 y=e^x\left(x^2+2 x-4\right)+c$

Solution

$\left(x^2+2\right) d y+2 x y d x=e^x\left(x^2+2\right) d x$ $\begin{aligned} & \left(x^2+2\right) d y=\left(e^x\left(x^2+2\right)-2 x y\right) d x \\ & \frac{d y}{d x}=\frac{e^x\left(x^2+2\right)}{x^2+2}-\frac{2 x}{x^2+2} y \\ & \frac{d y}{d x}+\frac{2 x}{x^2+2} y=e^x \\ & \mathrm{IF}=e^{\int \frac{2 x}{x^2+2} d x}=e^{\ln \left(x^2+2\right)} \\ & \mathrm{IF}=x^2+2 \\ & \therefore y \cdot \mathrm{IF}=\int \mathrm{Q} \cdot(\mathrm{IF}) d x+\mathrm{C} \\ & y \cdot\left(x^2+2\right)=\int e_{\text {II }}^x\left(x^2+2\right) d x+\mathrm{C} \\ & y\left(x^2+2\right)=\left(x^2+2\right) \cdot e^x-\int(2 x) \cdot e^x d x+\mathrm{C}\end{aligned}$ $\begin{aligned} & y\left(x^2+2\right)=e^x\left(x^2+2-2\right) \int x e^x d x+\mathrm{C} \\ & y\left(x^2+2\right)=e^x\left(x^2+2\right)-2\left[x \cdot e^x-\int e^x d x\right]+\mathrm{C} \\ & y\left(x^2+2\right)=e^x\left(x^2+2\right)-2 x e^x+2 e^x+\mathrm{C} \\ & y\left(x^2+2\right)=e^x\left(x^2-2 x+4\right)+\mathrm{C}\end{aligned}$

Asked in: MHT CET Full Test 2

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