#### Answer

$\frac{dy}{dx} = -5e^{-5x}$

#### Work Step by Step

$y = u^{-5}$
where,
$u = e^{x}$
Now,
$\frac{dy}{du} = -5u^{-6}$
and,
$\frac{du}{dx} = e^{x}$
So,
$\frac{dy}{dx} = \frac{dy}{du} \times \frac{du}{dx}$
$\frac{dy}{dx} = -5u^{-6} \times e^{x}$
$\frac{dy}{dx} = -5e^{-6x} \times e^{x}$
$\frac{dy}{dx} = -5e^{-5x}$