3.已知方程组 ) (x)_(1)+(x)_(2)+2(x)_(3)=a 3(x)_(1)-(x)_(2)-6(x)_(3)=a+2 (x)_(1)+4(x)_(2)+11(x)_(3)=a+3 .-|||-问a为何值时方程组有解?并在有解时求其通解.

1.已知方程组 ) (x)_(1)+(x)_(2)+(x)_(3)+(x)_(4)=2 3(x)_(1)+2(x)_(2)+(x)_(3)+(x)_(4)=a

9.已知方程组如下-|||- ) (x)_(1)-(x)_(2)=1, -(x)_(1)+(x)_(2)=2, 2(x)_(1)-2(x)_(2)=3, -3

线性方程组 ) (x)_(1)+2(x)_(2)-2(x)_(3)=1 2(x)_(1)+4(x)_(2)-4(x)_(3)=2 3(x)_(1)+6(x)_

已知非齐次线性方程组 ) (x)_(1)-5(x)_(2)+2(x)_(3)-3(x)_(4)=11 5(x)_(1)+3(x)_(2)+6(x)_(3)-(

3.求解线性方程组 ) (x)_(1)+2(x)_(2)-(x)_(3)+2(x)_(4)=1 2(x)_(1)+4(x)_(2)+(x)_(3)+(x)_(

例4 讨论线性方程组-|||- ) (x)_(1)+(x)_(2)+2(x)_(3)+3(x)_(4)=1 (x)_(1)+3(x)_(2)+6(x)_(3)

解方程组： ) (x)_(1)-(x)_(2)-(x)_(3)=2 2(x)_(1)-(x)_(2)-3(x)_(3)=1 3(x)_(1)+2(x)_(2)

方程组 ) (x)_(1)+(x)_(2)+2(x)_(3)=0 3(x)_(1)+4(x)_(2)=1 (x)_(2)-6(x)_(3)=1 .是自由变量

2.解方程组 ) (x)_(1)+(x)_(2)+(x)_(3) (x)_(1)+(x)_(2)-(x)_(3)-(x)_(4)=1 5(x)_(1)+5(

关于方程组_(1)-2(x)_(2)+3(x)_(3)-4(x)_(4)=4 _(1)-2(x)_(2)+3(x)_(3)-4