记A=
3-20-1
0221
1-2-3-2
0121
将(A,E)通过行变换化为(E,P)
P即为A的逆矩阵A^(-1)
(A,E)=
3-20-11000
02210100
1-2-3-20010
01210001
r1与r3交换
1-2-3-20010
02210100
3-20-11000
01210001
r3-3r1
1-2-3-20010
02210100
049510-30
01210001
r2与r4交换
1-2-3-20010
01210001
049510-30
02210100
r1+2r2,r3-4r2,r4-2r2
10100012
01210001
001110-3-4
00-2-1010-2
r1-r3,r2-2r3,r4+2r3
100-1-1046
010-1-2068
001110-3-4
000121-6-10
r1+r4,r2+r4,r3-r4
100011-2-4
0100010-2
0010-1-136
000121-6-10
所以A^(-1)=
11-2-4
010-2
-1-136
21-6-10