TeX Quellcode:

\begin{array}{rcll}r\left(-\sqrt{2}\right) &=& \sqrt{\dfrac{\left(-\sqrt{2}\right)^4}{2}}-\left(-\sqrt{2}\right) \\&=& \sqrt{2}+\sqrt{2} \\&=& 2\sqrt{2} \\&\neq& 0\end{array}