Primitive of Reciprocal of x squared by a x + b squared

Theorem

 * $\displaystyle \int \frac {\mathrm d x} {x^2 \left({a x + b}\right)^2} = \frac {-a} {b^2 \left({a x + b}\right)} - \frac 1 {b^2 x} + \frac {2 a} {b^3} \ln \left\vert{\frac {a x + b} x}\right\vert + C$