Primitive of Power of x over Power of Power of x plus Power of a

Theorem

 * $\displaystyle \int \frac {x^m \ \mathrm d x} {\left({x^n + a^n}\right)^r} = \int \frac {x^{m - n} \ \mathrm d x} {\left({x^n + a^n}\right)^{r - 1} } - a^n \int \frac {x^{m - n} \ \mathrm d x} {\left({x^n + a^n}\right)^r}$