Primitive of Reciprocal of Power of x by a x squared plus b x plus c

Theorem
Let $a \in \R_{\ne 0}$.

Then:
 * $\displaystyle \int \frac {\mathrm d x} {x^n \left({a x^2 + b x + c}\right)} = \frac {-1} {\left({n - 1}\right) c x^{n - 1} } - \frac b c \int \frac {\mathrm d x} {x^{n - 1} \left({a x^2 + b x + c}\right)} - \frac a c \int \frac {\mathrm d x} {x^{n - 2} \left({a x^2 + b x + c}\right)}$