系数矩阵=
1 -1 -1 1
1 -1 1 -3
1 -1 -2 3
r2-r1,r3-r1
1 -1 -1 1
0 0 2 -4
0 0 -1 2
r2*(1/2),r1+r2,r3+r2
1 -1 0 -1
0 0 1 -2
0 0 0 0
方程组的通解为:c1(1,1,0,0)'+c2(1,2,0,1)'.