Solution MINM.C40 Robert Beezer
The coefficient matrix and vector of constants for the system are \begin{align*} \begin{bmatrix} 1 & 1 & 3 & 1\\ -2 & -1 & -4 & -1\\ 1 & 4 & 10 & 2\\ -2 & 0 & -4 & 5 \end{bmatrix}&& \vect{b}=\colvector{5\\-7\\9\\9} \end{align*} $\inverse{A}$ can be computed by using a calculator, or by the method of Theorem CINM. Then Theorem SNCM says the unique solution is \begin{equation*} \inverse{A}\vect{b}= \begin{bmatrix} 38 & 18 & -5 & -2\\ 96 & 47 & -12 & -5\\ -39 & -19 & 5 & 2\\ -16 & -8 & 2 & 1 \end{bmatrix} \colvector{5\\-7\\9\\9} = \colvector{1\\-2\\1\\3} \end{equation*}