How do you integrate x3((x4)+3)5dx?

1 Answer
May 3, 2016

(x4+3)624+C

Explanation:

We have the integral

x3(x4+3)5dx

This can be solved fairly simply through substitution: we don't have to go through the hassle of expanding the binomial and then integrating term by term.

Let u=x4+3. This implies that du=4x3dx. Since we only have x3dx in the integral and not 4x3dx, multiply the interior of the integral by 4 and the exterior by 1/4 to balance this.

x3(x4+3)5dx=14(x4+3)54x3dx=14u5du

Integrating this results in (14)u66+C, and since u=x4+3, this becomes (x4+3)624+C.