For part i), my answer was $\begin{bmatrix}-1 & 2 & 0 \\ 2 & 5 & 1 \\0 & 1 & -5\end{bmatrix}$
But for part ii), when I try to calculate $\det(A-λI)=0$, it comes down to $-λ^3 -λ^2+29λ+45 =0$, which doesn't have a neat solution. I'm sure I've done something wrong here.