求下列向量组的秩和一个极大无关组,并把其余向量用此极大无关组线性表示.

A = (a1,a2,a3,a4) =
[1 2 -1 3]
[0 1 0 1]
[1 1 0 1]
[0 2 0 2]
行初等变换为
[1 1 0 1]
[0 1 -1 2]
[0 1 0 1]
[0 2 0 2]
行初等变换为
[1 1 0 1]
[0 1 -1 2]
[0 0 1 -1]
[0 0 2 -2]
行初等变换为
[1 1 0 1]
[0 1 -1 2]
[0 0 1 -1]
[0 0 0 0]
则向量组的秩为3,a1,a2,a3 为一个极大线性无关组.
再行初等变换为
[1 1 0 1]
[0 1 0 1]
[0 0 1 -1]
[0 0 0 0]
行初等变换为
[1 0 0 0]
[0 1 0 1]
[0 0 1 -1]
[0 0 0 0]
得 a4=a2-a3.