2 1 4 1
3 -1 2 1
1 3 0 1
4 0 7 2
r1+r2,r3+3r2得:
5 0 6 2
3 -1 2 1
10 0 6 4
4 0 7 2
按第二列展开得:
5 6 2
- 10 6 4
4 7 2
r2-2r1,r3-r1得:
5 6 2
- 0 -6 0
-1 1 0
按第三列展开得:
0 -6
-2
-1 1
=-2×(6-0)
=-12
2 1 4 1
3 -1 2 1
1 3 0 1
4 0 7 2
r1+r2,r3+3r2得:
5 0 6 2
3 -1 2 1
10 0 6 4
4 0 7 2
按第二列展开得:
5 6 2
- 10 6 4
4 7 2
r2-2r1,r3-r1得:
5 6 2
- 0 -6 0
-1 1 0
按第三列展开得:
0 -6
-2
-1 1
=-2×(6-0)
=-12