\left(
\begin{array}{ccccc}
 1 & 3 & b+4 & | & 8 \\
 0 & -7 & -2b-11 & | & -18 \\
 0 & 0 & -b & | & 2b \\
 0 & -3b-14 & -b^2-7b-22 & | & -8b-36
\end{array}
\right)