I'm trying to find the derivative of the following

$\displaystyle 5(e^{-0.01x}-e^{-0.51x})$

Since I thought the derivative of $\displaystyle e^x$ is $\displaystyle e^x$, I thought that the derivative of the above expression was just itself:

$\displaystyle 5(e^{-0.01x}-e^{-0.51x})$

If this is not right, how do I find out the derivative of some exponent with e?