45. Find the characteristic roots of the matrix A where A =

$$

\begin{bmatrix}

2 & 1 & -1 & 0 \\

0 & 2 & 1 & -1 \\

-1 & 0 & 2 & 1 \\

1 & -1 & 0 & 2

\end{bmatrix}

$$

.