Verify that $B$ is the inverse of $A$. \begin{align*} A&= \begin{bmatrix} 1 & 1 & -1 & 2\\ -2 & -1 & 2 & -3\\ 1 & 1 & 0 & 2\\ -1 & 2 & 0 & 2 \end{bmatrix} & B&= \begin{bmatrix} 4 & 2 & 0 & -1\\ 8 & 4 & -1 & -1\\ -1 & 0 & 1 & 0\\ -6 & -3 & 1 & 1 \end{bmatrix} \end{align*}