2-2r1,r3-3r1
1 -1 2 1 0
0 0 0 0 0
0 3 0 -4 1
0 3 0 0 1
r4-r3
1 -1 2 1 0
0 0 0 0 0
0 3 0 -4 1
0 0 0 4 0
交换行得
1 -1 2 1 0
0 3 0 -4 1
0 0 0 4 0
0 0 0 0 0
-->
1 0 2 0 1/3
0 1 0 0 1/3
0 0 0 1 0
0 0 0 0 0
2-2r1,r3-3r1
1 -1 2 1 0
0 0 0 0 0
0 3 0 -4 1
0 3 0 0 1
r4-r3
1 -1 2 1 0
0 0 0 0 0
0 3 0 -4 1
0 0 0 4 0
交换行得
1 -1 2 1 0
0 3 0 -4 1
0 0 0 4 0
0 0 0 0 0
-->
1 0 2 0 1/3
0 1 0 0 1/3
0 0 0 1 0
0 0 0 0 0