TeX source:
\begin{array}{rclcl} 0 &=& z^2-2z-8 &\vert& \text{p-q-Formel} \cr z_{1,2} &=& 1 \pm \sqrt{1+8} \cr &=& 1 \pm \sqrt{9} \cr &=& 1 \pm 3 \cr\cr z_1 &=& 1+3 = 4 \cr z_2 &=& 1-3 = -2 \end{array}