The integrating factor of \(x \frac{d y}{d x}+3 y=x^2\) is

The integrating factor of \(x \frac{d y}{d x}+3 y=x^2\) is
  1. \(\frac{3}{x}\)
  2. \(\log x\)
  3. \(x^3\)
  4. \(x\)

Solution

Given equation is, \(x \frac{d y}{d x}+3 y=x^2 \text { or } \frac{d y}{d x}+\frac{3}{x} \cdot y=x\) Comparing with, \(\frac{d y}{d x}+P y=Q,\) We have \(p=\frac{3}{x}\) and So, the integrating factor is, \(\mathrm{IF}=e^{\int p d x}=e^{\int \frac{3}{x} d x}=e^{3 \log x}=e^{\log x^3}=x^3\) \(r=\frac{d^{\prime}}{2}=\frac{0.8}{2}=0.4 \mathrm{~mm}=4 \times 10^{-4} \mathrm{~m}\) Hence, \(\Delta l=\frac{m g l}{\pi r^2 Y}=\frac{10 \times 10 \times 3}{\pi \times\left(4 \times 10^{-4}\right)^2 \times 10^{11}}\) \(=5.96 \times 10^{-3} \mathrm{~m}=0.596 \mathrm{~cm} \simeq 0.6 \mathrm{~cm}\)

Asked in: AP EAMCET 2020 (17 Sep Shift 2)

Practice more Differential Equations questions on Aicharya