增广矩阵 =
2 -1 1 1 1
1 2 -1 1 2
1 7 -4 11 5
r1-2r2,r3-r2
0 -5 3 -1 -3
1 2 -1 1 2
0 5 -3 10 3
r1+r3,r3*(1/5),r2-2r3
0 0 0 9 0
1 0 1/5 -3 4/5
0 1 -3/5 2 3/5
r1*(1/9),r2+3r1,r3-2r1
0 0 0 1 0
1 0 1/5 0 4/5
0 1 -3/5 0 3/5
交换行
1 0 1/5 0 4/5
0 1 -3/5 0 3/5
0 0 0 1 0
一般解为:(4/5,3/5,0,0)'+c(-1,3,5,0)'