TeX Quellcode:

\begin{array}{rclcl} P'(a) &=& 100-2a \cr\cr 0 &=& 100-2a &\vert& +2a \cr 2a &=& 100 &\vert& :2 \cr a &=& 50 \cr \cr b &=& 100-50 = 50 \end{array}