TeX Quellcode:
\begin{array}{rcl} -(2a+d)(-2d+a) &=& -(-4a \cdot d+2a \cdot a-2d \cdot d+a \cdot d) \cr &=& -(-3a \cdot d+2a \cdot a-2d \cdot d) \cr &=& -2a \cdot a+3a \cdot d+2d \cdot d \end{array}