TeX Quellcode:

\begin{array}{rcl} f'_z(x,y,z) &=& xy^2 e^{-3xy}\cdot\dfrac{1}{z} \\\\ &=& \dfrac{xy^2 e^{-3xy}}{z} \\\\ &=& xy^2 e^{-3xy}\cdot z^{-1} \end{array}