Chapter 2.4, Problem 26E

In Exercises 23–26, use the fact that the following two matrices are inverses of each other to solve the system of linear equations.

$\left[\begin{array}{cccc}9& 0& 2& 0\\ -20& -9& -5& 5\\ 4& 0& 1& 0\\ -4& -2& -1& 1\end{array}\right]$ and $\left[\begin{array}{cccc}1& 0& -2& 0\\ 0& 1& 0& -5\\ -4& 0& 9& 0\\ 0& 2& 1& -9\end{array}\right]$

$\{\begin{array}{c}x-2z=-1\\ y-5w=0\\ -4x+9z=0\\ 2y+z-9w=1\end{array}$