2 ( 1)2 2 24 2
解 1 ( 12) 1 ( 1)1 2 12
3 3 ( 1)3 2 36
131 0 12 2140 (4) 1 31
1 134 40 2
131
0 12 6 78 2140 解 1 31 20 5 6
1 134
40 2
a11a12a13 x1
(5)(x1x2x3) a12a22a23 x2
aaa 132333 x3
解
a11a12a13 x1
(x1x2x3) a12a22a23 x2
aaa 132333 x3
x1
(a11x1 a12x2 a13x3 a12x1 a22x2 a23x3 a13x1 a23x2 a33x3) x2
x 3
5 设A
22
a11x12 a22x2 a33x3 2a12x1x2 2a13x1x3 2a23x2x3
1
12 B 1
13 0 问
2
(1)AB BA吗? 解 AB BA 因为AB
3
44 BA 1
36 2 所以AB BA
8
(2)(A B)2 A2 2AB B2吗?