TeX source:
\begin{array}{rclcl} 0 &=& x^2-2x-3 &\vert& \text{p-q-Formel} \cr x_{3,4} &=& 1\pm\sqrt{(-1)^2+3} \cr x_{3,4} &=& 1\pm\sqrt{4} \cr\cr x_3 &=& 1+2 = 3 \cr x_4 &=& 1-2 = -1 \cr\cr\mathbb{L} &=& \left\{-2;-1;2;3\right\}\end{array}