A certain 4x4 real matrix is known to have these properties:
1) Two of the eigenvalues of A are L1= 3 and L2= 2.
2) The number 3 is an eigenvalue of the matrix A + 2I.
3) det. A = 12.
What are the other 2 eigenvalues of A and what is the characteristic polynomial of A, At, and A-1?