TeX source:
\begin{array}{rclcl} z_1 = x^2 &=& 4 & \vert & \pm\sqrt{} \cr x_{2,3} &=& \pm \sqrt{4} \cr x_2 &=& 2 & & \rightarrow \quad P_2(2 \mid 9) \cr x_3 &=& -2 & & \rightarrow \quad P_3(-2 \mid 9) \cr\cr z_2 = x^2 &=& -2 & \vert & \pm\sqrt{} \cr x_{4,5} &=& \pm\sqrt{-2} \end{array}