If $x^y=e^{x-y}$, then $\frac{dy}{dx}=$
Answer & explanation
Correct answer: option 2
$x^y=e^{x-y}$
Take $log_e$ on both sidees
$log_ex^y=log_ee^{x-y}⇒ ylogx=(x−y)log_ee $
$ylogx=x−y$ ....(i)
$y[logx+1]=x$ ....(ii)
Differentiate both sides w.r.t. x
$\frac{dy}{dx}[1+logx]y[\frac{1}{x}]=1$
$\frac{dy}{dx}=\frac{1-\frac{y}{x}}{1+logx}$
from eq. (ii) $\frac{y}{x}=\frac{1}{(1+logx)}$
$\frac{dy}{dx}=\frac{1-\frac{1}{1+logx}}{1+logx}=\frac{logx}{(1+logx)^2}$