0 1 1 -1 2
0 2 -2 -2 0
0 -1 -1 1 1
1 1 0 1 -1
→
1 1 0 1 -1
0 1 1 -1 2
0 2 -2 -2 0
0 -1 -1 1 1
→
1 1 0 1 -1
0 1 1 -1 2
0 0 -4 0 -4
0 0 0 0 3
→
1 1 0 1 -1
0 1 1 -1 2
0 0 1 0 1
0 0 0 0 1
故秩等于4