因式分解即可:
|λI-A| =
λ -2 2
-2 λ-4 -4
2 -4 λ+3
=
λ -2 2
0 λ-8 λ-1
2 -4 λ+3
=
λ 0 2
0 2λ-9 λ-1
2 λ-1
λ+3
=
λ 0 2
0 2λ-9 λ-1
2 8-λ
4
=
λ 0 2
0 2λ-9 λ-1
2-2λ 8-λ
0
= λ(λ-1)(λ-8)+4(2λ-9)(λ-1)
= (λ-1)(λ(λ-8)+4(2λ-9))
= (λ-1)(λ+6)(λ-6)
= 0
解得λ=1,-6,6