TeX source:
\begin{array}{crclcl} & x\left(\dfrac{31}{20}x-\dfrac{7}{40}\right)-x^2 &=& 0 \cr\cr & \dfrac{31}{20}x^2-\dfrac{7}{40}x-x^2 &=& 0 & \vert & \cdot 40 \cr\cr & 62x^2-7x-40x^2 &=& 0 \cr & 22x^2-7x &=& 0 \cr & x(22x-7) &=& 0 \cr \text{Faktor 1:} & x_1 &=& 0 \cr\cr \text{Faktor 2:} & 22x-7 &=& 0 &\vert& +7 \cr & 22x &=& 7 &\vert& :22 \cr & x_2 &=& \dfrac{7}{22} \cr\cr & \mathbb{L} &=& \left\{0;\dfrac{7}{22}\right\} \end{array}