4. 设向量组 (alpha )_(1)=((0,1,1))^T, (alpha )_(2)=((1,0,1))^T (alpha )_(3)=((2,1,0))^T (alpha )_(4)=((1,1,1))^T-|||-(1)求向量组的秩;-|||-(2)求此向量组的一个极大无关组,并把其余向量用所求的极大无关组线性表