TeX Quellcode:

\begin{array}{rcl} f(7) &=& \dfrac{7}{8} \sqrt{-63\cdot 7+9\cdot 7^2} \\\\ &=& \dfrac{7}{8} \sqrt{-441+441} \\\\ &=& \dfrac{7}{8} \sqrt{0} \\\\ &=& 0\end{array}