I've calculated the following eigen value and determined the following matrix:

eigenvalue, U= -5

Original matrix

([-5-U] 2 -3)

(0 [1-U] -2)

(0 1 [4-U])

Solved Matrix:

(0 0 28)0

(0 3 -1)0

(0 0 0) 0

I'm not exactly clear on how to determined the eigenvector