# How do you use substitution to integrate #e^ (-5x) dx#?

##### 1 Answer

May 25, 2015

Here are two solutions:

**The "usual way"** (as far as my experience), is to turn this into an integral of the form

Let

If you want to be different, turn it into

We know that

**Alternative Method**

If we want to make

Now with the substitution:

we get

Which is equal to the answer by the more usual method.