Giải hệ phương trình tuyến tính (left{ begin{array}{l}

mathop {2x}nolimits_1 + 7mathop xnolimits_2 + 3mathop xnolimits_3 + mathop xnolimits_4 = 5\

mathop xnolimits_1 + 3mathop xnolimits_2 + 5mathop xnolimits_3 – 2mathop xnolimits_4 = 3\

mathop xnolimits_1 + mathop {5x}nolimits_2 – 9mathop xnolimits_3 + 8mathop xnolimits_4 = 1\

5mathop xnolimits_1 + 18mathop xnolimits_2 + mathop {4x}nolimits_3 + 5mathop xnolimits_4 = 12

end{array} right.)

A. (mathop xnolimits_1 = 2 + mathop xnolimits_3 + 7mathop xnolimits_4 ,x2 = – 1 + 5mathop xnolimits_3 – mathop xnolimits_4 )

B. (mathop xnolimits_1 = 6 – 26mathop xnolimits_3 + 17mathop xnolimits_4 ,x2 = – 1 + 7mathop xnolimits_3 – mathop {5x}nolimits_4 )

C. (mathop xnolimits_1 = 2 + 6mathop xnolimits_3 – 7mathop xnolimits_4 ,x2 = – 1 + 4mathop xnolimits_3 – mathop {2x}nolimits_4)

D. (mathop xnolimits_1 = 4 + 11mathop xnolimits_4 ,x2 = – 1 – 6mathop xnolimits_4 ,mathop xnolimits_3 = 2)

Hướng dẫn

Chọn B là đáp án đúng