TeX Quellcode:

\begin{array}{rcl}\mathbb{D}&=&\mathbb{R}\setminus_{\{0\}} \cr \cr f(x) &=& x^{-2} \cr \cr \cr f'(x) &=& -2 \cdot x^{-2-1} \cr &=& -2\cdot x^{-3} \cr \cr &=& -\dfrac{2}{x^3} \end{array}