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}