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MHT CET · Maths · Differential Equations

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

  1. A \(\frac{x}{\mathrm{e}^x}\)
  2. B \(x e^x\)
  3. C \(\mathrm{e}^x\)
  4. D \(\frac{\mathrm{e}^x}{x}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{\mathrm{e}^x}{x}\)

Step-by-step Solution

Detailed explanation

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