(4 2)(x x)-(5 2)于是Xi = A-1即[AX = EkXi2 = 0AXi2 = 0UX21 = -B-'CA-1CX + BX21 = 0X2 = 0BX2 = E,A-1D-1B-1(-B-ICA-184.5矩阵的分块§4.5 矩阵的分块 ( ) 11 12 21 22 0 0 , 0 k r A X X E C B X X E       =       于是 即 11 12 11 21 22 0 0 k r AX E AX CX BX BX E  =   =   + =    = 1 1 1 1 1 A 0 D B CA B − − − − −    =     − . 1 11 12 1 1 21 22 0 0 X A X X B CA X − − −  =   =   = −    =