Primitive of Reciprocal of a x squared plus b x plus c/c equal to 0

Theorem
Let $a, b \in \R_{\ne 0}$. Let $c = 0$.

Then:
 * $\displaystyle \int \frac {\d x} {a x^2 + b x + c} = \frac 1 b \ln \size {\frac x {a x + b} } + C$