(3) A = 3E + B, 其中 B = [0 1 0] [0 0 1] [0 0 0] 则 B^2 = [0 0 1] [0 0 0] [0 0 0] B^3 = O 于是 A^3 = (3E+B)^3 = 27E + 27B + 9B^2 + B^3 = [27 27 9] [0 27 27] [0 0 27]5591
