For matrix A$\displaystyle =\begin{pmatrix}-4 & 1 & 1\\1 & 5 & -1\\0 & 1 & -3\end{pmatrix}$

a) Find the characteristic polynomial of A

b) Find the eigenvalues of A

c) Find the eigenvectors of A

d) If A is diagonalizable, find a matrix P such that $\displaystyle P^{-1}AP$ is diagonal

I am stressing out because I really am not understanding any of this. Thank you in advance for any help!