TeX Quellcode:

\begin{array}{crcrcrcrl} \text{I} & 3x_1 &-& 6x_2 &+& 9x_3 &=& 21 \cr \text{II} & -x_1 &+& 2x_2 &+& 4x_3 &=& 21 \cr \text{III} & -x_1 & & &+& 5x_3 &=& 21 \cr \cr \text{I} & 3x_1 &-& 6x_2 &+& 9x_3 &=& 21 \cr \text{I + 3II} & & & & & 21x_3 &=& 84 &\Rightarrow x_3=4 \cr \text{III} & -x_1 & & &+& 5x_3 &=& 21 \cr\cr x_3=4 \text{ in III} & -x_1 & & &+& 5\cdot 1 &=& 21 &\Rightarrow x_1=-1 \cr x_1=-1 \text{ und } x_3=4 \text{ in I} & 3\cdot (-1) &-& 6 \cdot x_2 &+& 9\cdot 4 &=& 21 &\Rightarrow x_2=2 \end{array}