# Integration by Parts

Use integration by parts when the integrand factors into two things that both include the variable, but integration by substitution doesn't work!

### Sample Problem

We can use integration by parts on

because we can factor the *x*^{2} to get

and choose *u* = *x* and *v'* = *xe*^{x2}.

### Sample Problem

We wouldn't use integration by parts on

because this integral begs for substitution.