矩阵，R的三次方怎么是这样算的，这不是才二次方吗

Question

如题所述

Answer 1

记原矩阵为A
则 A = E - (1/n) D
其中D是元素全为1的n阶矩阵.
因为 D^2 = nD --乘一下就知道了
所以 A^2 = [E- (1/n) D]^2
= E - (2/n)D + (1/n^2)D^2
= E - (2/n)D + (1/n)D
= E - (1/n)D
= A.