|λE-A| =|λ-1 1||-2 λ-4|= λ^2-5λ+6 = (λ-2)(λ-3)特征值 λ = 2,3。对 λ = 2,λE-A =[1 1][-2 -2]初等行变换为[1 1][0 0]特征向量为 (1, -1)^T;对 λ = 3,λE-A =[2 1][-2 -1]初等行变换为[2 1][0 0]特征向量为 (1, -2)^T.