\left(
\begin{array}{cccc}
 1 & -1 & | & 1 \\
 2 & 5 & | & 9
\end{array}
\right)\sim \left(
\begin{array}{cccc}
 2 & 5 & | & 9 \\
 1 & -1 & | & 1
\end{array}
\right)