Primitive of Reciprocal of a x + b cubed/Proof 2

Proof
From Primitive of Power of $a x + b$:
 * $\displaystyle \int \left({a x + b}\right)^n \ \mathrm d x = \frac {\left({a x + b}\right)^{n + 1} } {\left({n + 1}\right) a} + C$

where $n \ne 1$.

The result follows by setting $n = -3$.