1 1 4 4 1 1 4 4 1 1 4 4 1 0 3 0 x1+ 3x3 = 0
-1 4 1 16 0 5 5 20 0 1 1 4 0 1 1 4 x2+x3 = 4
1 -1 2 -4 0 -2 -2 -8 0 1 1 4 0 0 0 0
经过消法变换,方程组只有两个方程了：3个未知数两个方程有无穷多组
x1=-3x3 (1)
x2=4-x3 (2)
x3=x3 (3)
(1)(2)(3) 为原线性方程组的解.