TeX source:

\begin{array}{rclll} \dfrac{2x^2-4x+4}{x^3-10x^2+27} &=& 0 & \vert & \cdot\left(x^3-10x^2+27x\right) \cr\cr 2x^2-4x+4 &=& 0 & \vert & \text{a-b-c-Formel} \cr\cr x_{1,2} &=& \dfrac{4\pm\sqrt{16-32}}{4} \cr\cr x_{1,2} &=& \dfrac{4\pm\sqrt{-16}}{4} \end{array}