Giải hệ phương trình tuyến tính ⎧ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎩ 2 x 1 − x 2 + 3 x 3 + 4 x 4 = 5 4 x 1 − 2 x 2 + 5 x 3 + 6 x 4 = 7 6 x 1 − 3 x 2 + 7 x 3 + 8 x 4 = 9 3 x 1 − 4 x 2 + 9 x 3 + 10 x 4 = 11

\[{{\rm{x}}_1} = 1,{{\rm{x}}_2} = 3 - 2{{\rm{x}}_4},{{\rm{x}}_3} = 4 - 2{{\rm{x}}_4}\]

\[{{\rm{x}}_1} = 0,{{\rm{x}}_2} = 4 - 2{{\rm{x}}_4},{{\rm{x}}_3} = 3 - 2{{\rm{x}}_4}\]

\[{{\rm{x}}_1} = 1,{{\rm{x}}_2} = 3 - 2{{\rm{x}}_3},{{\rm{x}}_3} = 4 + 2{{\rm{x}}_3}\]

\[{{\rm{x}}_1} = 3 + 5{{\rm{x}}_4},{{\rm{x}}_2} = 4,{{\rm{x}}_3} = 3 - {{\rm{x}}_4}\]