(a1,a2,a3,a4)=
1 2 1 3
4 9 0 10
1 -1 -3 -7
0 -3 -1 -7
r2-4r1,r3-r1
1 2 1 3
0 1 -4 -2
0 -3 -4 -10
0 -3 -1 -7
r4-r3,r1-2r2,r3+3r2
1 0 9 7
0 1 -4 -2
0 0 -16 -16
0 0 3 3
r4*(1/3),r1-9r4,r2+4r4,r3+16r4
1 0 0 -2
0 1 0 2
0 0 0 0
0 0 1 1
所以向量组的秩为 3
a1,a2,a3 是一个极大无关组
且 a4 = -2a1+2a2+a3