If $x^y=e^{x-y}$, then $\frac{d y}{d x}=$
- $\frac{\log x}{1+\log x}$
- $\frac{\log x}{x(1+\log x)^2}$
- $\frac{\log x}{(1+\log x)^2}$
- $\frac{x \log x}{(1+\log x)^2}$
Solution
$\begin{aligned} & \Rightarrow \frac{d y}{d x} \log x+y \cdot \frac{1}{x}=1-\frac{d y}{d x} \\ & \Rightarrow \frac{d y}{d x}=\frac{x-y}{x(1+\log x)} \\ & \Rightarrow \frac{d y}{d x}=\frac{\log x}{(1+\log x)^2} \quad\left[\text { Putting } y=\frac{x}{1+\log x} \text { from (i)] }\right.\end{aligned}$Asked in: MHT CET 2022 (07 Aug Shift 1)