Primitive of x cubed over a x + b cubed

Theorem

 * $\displaystyle \int \frac {x^3 \ \mathrm d x} {\left({a x + b}\right)^3} = \frac x {a^3} - \frac {3 b^2} {a^4 \left({a x + b}\right)} + \frac {b^3} {2 a^4 \left({a x + b}\right)^2} - \frac {3 b} {a^4} \ln \left\vert{a x + b}\right\vert + C$

Proof
Put $u = a x + b$.

Then:

Then: