$\left \{ {{x+2y-1=0} \atop {2x+y-5=0}} \right.$ $⇔\left \{ {{x+2y=1} \atop {4x+2y=10}} \right.$ $⇔\left \{ {{-3x=-9} \atop {x+2y=1}} \right.$ $⇔\left \{ {{x=3} \atop {3+2y=1}} \right.$ $⇔\left \{ {{x=3} \atop {y=-1}} \right.$ Bình luận
⇔ 2x +4y =2
2x +y = 5
⇔ 3y = -3
2x + y=5
⇔ y =-1
2x -1 =5
⇔ x =3
y =-1
$\left \{ {{x+2y-1=0} \atop {2x+y-5=0}} \right.$
$⇔\left \{ {{x+2y=1} \atop {4x+2y=10}} \right.$
$⇔\left \{ {{-3x=-9} \atop {x+2y=1}} \right.$
$⇔\left \{ {{x=3} \atop {3+2y=1}} \right.$
$⇔\left \{ {{x=3} \atop {y=-1}} \right.$