TeX source:
\begin{array}{rclcl}\dfrac{3}{4}z^2+2z-4 &=& 0 &\vert & :\dfrac{3}{4} \\z^2+\dfrac{8}{3}z-\dfrac{16}{3} &=& 0 &\vert & \text{p-q-Formel} \\z_{1,2} &=& -\dfrac{4}{3}\pm\sqrt{\left(\dfrac{4}{3}\right)^2+\dfrac{16}{3}} \\\\z_{1,2} &=& -\dfrac{4}{3}\pm\sqrt{\dfrac{64}{9}} \\\\z_1 &=& -\dfrac{4}{3}+\dfrac{8}{3} = \dfrac{4}{3} \\z_2 &=& -\dfrac{4}{3}-\dfrac{8}{3} = -4 \end{array}