写出向量组为1 1 5 11 1 -2 23 -1 7 -51 3 9 5 r2-r1,r3-3r1,r4-r1~1 1 5 10 0 -7 10 -4 -8 -80 2 4 4 r3/(-4),r4-2r3,r1-r3,交换r2和r3~1 0 3 -10 1 2 20 0 -7 10 0 0 0 r3/(-7),r1-3r3,r2-2r3~1 0 0 -4/70 1 0 16/70 0 1 -1/70 0 0 0显然向量组是线性相关的4/7 a1 -16/7 a2 +1/7 a3 -a4=0设向量组a1=(1,1,3,1) a2=(1,1,-1,3) a3=(5,-2,7,9) a4=(1,2