TeX Quellcode:
\begin{array}{rcl} \dfrac{2}{3a-9} + \dfrac{b}{-3+a} &=& \dfrac{2}{3\left(a-3\right)} + \dfrac{b}{a-3} \cr \cr &=& \dfrac{2}{3\left(a-3\right)} + \dfrac{3b}{3\left(a-3\right)} \cr \cr &=& \dfrac{2+3b}{3\left(a-3\right)}\end{array}