Integrating

You're going to like this part. Since
,
we know immediately that:

In other words, if *e*^{x} is its own mother, then it's its own child, too.

Now, we can find lots of other integrals using substitution. For instance,

(You know, *u*=3*x*, *du*=3*dx*, etc. Usual drill.)

More generally, it's worth remembering that:

We could also use substitution or eyeball to see that