# Math Help - Super Easy quick question!

1. ## Super Easy quick question!

What is the derivative of $e^{-u}$ ???

It seems so simple yet I always struggle with it.

2. Ok, it's $e^{-u}\cdot du$

What is the derivative of $e^{-u}$ ???
You've neglected an extremely important piece of information .... derivative of $e^{-u}$ with respect to what variable? u? x?
The derivative of $e^{-u}$ with respect to u is $-e^{-u}$.
The derivative of $e^{-u}$ with respect to x is $-e^{-u} \, \frac{du}{dx}$.