TeX source:
\begin{array}{rclcl} x^2-49 &=& 0 & \vert & +49 \cr x^2 &=& 49 & \vert & \pm \sqrt{} \cr x &=& \pm \sqrt{49} \cr\cr x_1 &=& 7 \cr x_2 &=& -7 \end{array}