TeX source:
f(x)= \left\vert -2x^2-20x+78 \right\vert=\left\{\begin{array}{rll}-2x^2-20x+78 & \text{ für } & x\geq0 \cr-\left(-2x^2-20x+78\right) = 2x^2+20x-78 & \text{ für } & x < 0\end{array} \right.