The particular solution of the differential equation $y\left(\frac{\mathrm{d} x}{\mathrm{~d} y}\right)=x…

The particular solution of the differential equation $y\left(\frac{\mathrm{d} x}{\mathrm{~d} y}\right)=x \log x$ at $x=\mathrm{e}$ and $\mathrm{y}=1$ is
  1. $\mathrm{e}^{x y}=2$
  2. $x=\mathrm{e}^{\mathrm{y}}$
  3. $x\mathrm{y}=2$
  4. $\log x=2 y$

Solution

$y\left(\frac{d x}{d y}\right)=x \cdot \log x$ $\therefore \int \frac{1}{x \cdot \log x} d x=\int \frac{1}{y} d y$ $\therefore \log |\log x|=\log y+\log c$ We have $x=e$ and $y=1$ $\therefore \log |\log e|=\log 1+\log c \Rightarrow \log c=0$ $\therefore \log |\log x|=\log y \Rightarrow \log x=y \Rightarrow x=e^{y}$

Asked in: MHT CET 2020 (16 Oct Shift 2)

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