解: (a1,a2,a3,a4) =
1 -1 3 -2
1 -3 2 -6
1 5 -1 10
3 1 p+2 p
r3-r1-r2-r3, r3-r2,r2-r1
1 -1 3 -2
0 -2 -1 -4
0 8 -3 16
0 0 p-2 p-2
r3+4r2
1 -1 3 -2
0 -2 -1 -4
0 0 -7 0
0 0 p-2 p-2
r3*(-1/7),r1-3r3,r2+r3,r4-(p-1)r3
1 -1 0 -2
0 -2 0 -4
0 0 1 0
0 0 0 p-2
当p=2时, r(a1,a2,a3,a4)=3, a1,a2,a3,a4线性相关, a1,a2,a3 是一个极大无关组.