Câu 5:
Giải hệ phương trình tuyến tính {2x1−x2+x3−x4=34x1−2x2−2x3+3x4=22x1−x2+5x3−6x4=12x1−x2−3x3+4x4=5\left\{ \begin{array}{l}\mathop {2x}\nolimits_1 - \mathop x\nolimits_2 + \mathop x\nolimits_3 - \mathop x\nolimits_4 = 3\\\mathop {4x}\nolimits_1 - 2\mathop x\nolimits_2 - 2\mathop x\nolimits_3 + 3\mathop x\nolimits_4 = 2\\\mathop {2x}\nolimits_1 - \mathop x\nolimits_2 + 5\mathop x\nolimits_3 - 6\mathop x\nolimits_4 = 1\\2\mathop x\nolimits_1 - \mathop x\nolimits_2 - \mathop {3x}\nolimits_3 + 4\mathop x\nolimits_4 = 5\end{array} \right.⎩⎨⎧2x1−x2+x3−x4=34x1−2x2−2x3+3x4=22x1−x2+5x3−6x4=12x1−x2−3x3+4x4=5
