How do you evaluate the integral inte^(4x) dxe4xdx?

1 Answer
Aug 13, 2014

We will use uu-substitution, letting u = 4xu=4x.

Thus, du = 4dxdu=4dx.

Also, we will use the constant law of integration, namely int C*f(x)dx = C*int f(x) dxCf(x)dx=Cf(x)dx to rewrite the integral so that it contains dudu:

int e^(4x)dx = 1/4 int 4*e^(4x)dxe4xdx=144e4xdx

Now, we will rewrite in terms of uu:

int e^(4x)dx = 1/4 int e^(u)due4xdx=14eudu

We know that the integral of e^u dueudu will simply be e^ueu. Remember the constant of integration:

int e^(4x)dx = 1/4 e^(u) + Ce4xdx=14eu+C

Substituting back uu gives:

int e^(4x)dx = 1/4 e^(4x) + Ce4xdx=14e4x+C