(a1^T,a2^T,a3^T,a4^T)=
2 3 4 4
1 -1 2 -3
3 2 6 1
-1 0 -2 1
r1+2r4,r2+r4,r3+3r4
0 3 0 6
0 -1 0 -2
0 2 0 4
-1 0 -2 1
r1+3r2,r3+2r2
0 0 0 0
0 -1 0 -2
0 0 0 0
-1 0 -2 1
所以 r(a1,a2,a3,a4)=2
(a1^T,a2^T,a3^T,a4^T)=
2 3 4 4
1 -1 2 -3
3 2 6 1
-1 0 -2 1
r1+2r4,r2+r4,r3+3r4
0 3 0 6
0 -1 0 -2
0 2 0 4
-1 0 -2 1
r1+3r2,r3+2r2
0 0 0 0
0 -1 0 -2
0 0 0 0
-1 0 -2 1
所以 r(a1,a2,a3,a4)=2