a1=(1,1,-1,1)
a2=(3,2,-4,4)
a3=(2,3,-4,5)
a4=(5,4,-6,6)
竖着写成矩阵
1 3 2 5
1 2 3 4
-1 -4 -4 -6
1 4 5 6
然后做行变换
1 3 2 5
0 -1 1 -1
0 -1 -2 -1
0 1 3 1
1 3 3 5
0 -1 1 -1
0 0 -3 0
0 0 4 0
1 3 0 5
0 -1 0 -1
0 0 1 0
0 0 0 0
1 0 0 2
0 1 0 1
0 0 1 0
0 0 0 0
显然秩是3啰,a1、a2、a3即是一个极大无关组