If $ A = \begin{bmatrix} 1 & 2 & 2 \\[0.3em] 2 & 1 & 2 \\[0.3em] 2 & 2 & 1 \end{bmatrix}$ what is $ A^2-4A-5I=0$

Question

$\begin{array}{1 1} 1 \\ 2 \\ 0 \\ 3 \end{array} $