TeX Quellcode:
\begin{array}{rclcl} \sqrt{x^2+13} &=& 7 &\vert& ()^2 \cr x^2+13 &=& 49 &\vert& -13 \cr x^2 &=& 36 &\vert& \pm\sqrt{} \cr\cr x_1 &=& 6\;\in\;\mathbb{D} \cr x_2 &=& -6\;\in\;\mathbb{D} \end{array}