利用分块矩阵乘法,计算AB.
A=
(A1
A2
A3)
,B=(B1,B2,B3).其中,A1=(-2,-1,2),A2=(2,-2,1),A3=(1,2,2),
B1=
(-2
-1
2),
B2=
(2
-2
1),
B3=
(1
2
2)
AB= (A1 A2 A3) (B1,B2,B3) = (A1B1 A1B2 A1B3 A2B1 A2B2 A2B3 A3B1 A3B2 A3B3) A1B1=(-2,-1,2) (-2 -1 2) =9,A1B2=(-2,-1,2) (2 -2 1) =0,A1B3=(-2,-1,2) (1 2 2) =0. 同理,A2B1=0,A2B2=9,A2B3=0,A3B1=0,A3B2=0,A3B3=9, 则AB= (9 0 0 0 9 0 0 0 9)