TeX source:
\begin{array}{rclcl}5z^2+11z+2 &=& 0 &\vert& \text{a-b-c-Formel} \\z_{1,2} &=& \dfrac{-11 \pm \sqrt{11^2-4 \cdot 5 \cdot 2}}{2\cdot 5} \\\\&=& \dfrac{-11 \pm \sqrt{81}}{10} \\\\z_{1} &=& \dfrac{-11 + 9}{10} = -\dfrac{1}{5}\\\\z_{2} &=& \dfrac{-11 - 9}{10} =-2\\\\\end{array}