TeX source:
\begin{array}{rclll} \dfrac{x^2+2x-30}{x-3} &=& 2 & \vert & \cdot(x-3) \cr x^2+2x-30 &=& 2(x-3) \cr x^2+2x-30 &=& 2x-6 & \vert & -2x+30 \cr x^2 &=& 24 & \vert & \pm\sqrt{} \cr\cr x_1 &=& \sqrt{24} \;\in\;\mathbb{D} \cr x_2 &=& -\sqrt{24} \;\in\;\mathbb{D} \cr\cr\mathbb{L} &=& \left\{-\sqrt{24};\sqrt{24}\right\} \end{array}