TeX Quellcode:

\begin{array}{rclcl} -217 &=& 7 (x^2-4x) \cr -217 &=& 7x^2-28x &\vert& +217 \cr0 &=& 7x^2-28x+217 &\vert& : 7 \cr0 &=& x^2-4x+31 &\vert& \text{p-q-Formel} \cr x_{1,2} &=& 2 \pm \sqrt{\left(-2\right)^2-31} \cr &=& 2\pm \sqrt{-27} \cr &=& 2 \pm \sqrt{9\cdot 3 \cdot (-1)} \cr &=& 2\pm 3 \cdot \sqrt{3} \sqrt{-1} &\vert& \sqrt{-1}=i \cr \cr x_1 &=& 2+3\sqrt{3} i \cr x_2 &=& 2-3\sqrt{3} i \cr \cr \mathbb{L} &=& \left\{2+3\sqrt{3}i \; ; \; 2-3\sqrt{3}i \right\}\end{array}