TeX Quellcode:

\begin{array}{rclcl} 21 x+125 &=& x^2+3x+215 &\vert& -21x-125 \cr 0 &=& x^2-18x+90 &\vert& \text{p-q-Formel} \cr x_{1,2} &=& 9\pm \sqrt{9^2-90} \cr &=& 9\pm \sqrt{-9} \cr &=& 9\pm \sqrt{-1\cdot 9} \cr&=& 9\pm 3 \sqrt{-1} &\vert& \sqrt{-1}=i \cr \cr x_1&=&9+3i \cr x_2 &=& 9-3i \cr \cr \mathbb{L} &=& \{9+3i \; ; \; 9-3i\}\end{array}