Integrating factor of the differential equation $\frac{\mathrm{d} y}{\mathrm{~d} x}+y=\frac{1+y}{x}$ is

Integrating factor of the differential equation $\frac{\mathrm{d} y}{\mathrm{~d} x}+y=\frac{1+y}{x}$ is
  1. $\frac{x}{\mathrm{e}^x}$
  2. $x e^x$
  3. $\mathrm{e}^x$
  4. $\frac{\mathrm{e}^x}{x}$

Solution

$\begin{array}{ll} & \frac{\mathrm{d} y}{\mathrm{~d} x}+y=\frac{1+y}{x} \\ & \Rightarrow \frac{\mathrm{~d} y}{\mathrm{~d} x}+y=\frac{1}{x}+\frac{y}{x} \\ & \Rightarrow \frac{\mathrm{~d} y}{\mathrm{~d} x}+\left(1-\frac{1}{x}\right) y=\frac{1}{x} \\ \therefore \quad & \text { I.F. }=\mathrm{e}^{\int\left(1-\frac{1}{x}\right) \mathrm{dx}}=\mathrm{e}^{x-\log x}=\frac{\mathrm{e}^x}{x}\end{array}$

Asked in: MHT CET 2024 (09 May Shift 2)

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