Integrate.

Answer

Let

*u* = *e*^{4x}

*u*' = 4*e*^{4x}

We need to introduce the factor 4 to the integrand, so we multiply the integrand by 4 and the outside of the integral by .

Those parentheses in the second-to-last step are important. If we had written

instead of

we would have gotten the wrong answer!