what is the derivative of e^(x)-1?
$\displaystyle y = e^x - 1$
$\displaystyle \frac{dy}{dx} = e^x$
$\displaystyle y = e^{x-1}$
$\displaystyle \frac{dy}{dx} = e^{x-1}$
in general ...
$\displaystyle \frac{d}{dx} [e^u] = e^u \cdot \frac{du}{dx}$
where $\displaystyle u$ is a function of $\displaystyle x$