r1-3r3
0 4 9 5
0 2 2 1
1 -2 -3 -2
0 1 2 1
r1-4r4,r2-2r4,r3+2r4
0 0 1 1
0 0 -2 -1
1 0 1 0
0 1 2 1
r2+2r1,r3-r1,r4-2r1
0 0 1 1
0 0 0 1
1 0 0 -1
0 1 0 -1
r1-r2,r3+r2,r4+r2
0 0 1 0
0 0 0 1
1 0 0 0
0 1 0 0
交换行
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1