求解1123 3-1-1-2 23-1-1

|1 1 2 3|

3 -1 -1 -2

2 3 -1 -1

1 2 3 -1

=|1 1 2 3|

0 -4 -7 -11 【r2-r1*3

0 1 -5 -7 r3-r1*2

0 1 1 -4 r4-r1

=|1 1 2 3|

0 0 -3 -27 【r2+r4*4

0 0 -6 -3 r3-r4

0 1 1 -4

=|1 1 2 3|

0 0 -3 -27

0 0 0 51 【r3-r2*2

0 1 1 -4

=|1 1 2 3|

0 1 1 -4 【r4与r3交换、r3与r2交换，两次交换行列式符号不变

0 0 -3 -27

0 0 0 51

=-153