Bună!
[tex]b) \left \{ {{x-y=4/*2} \atop {x+2y=1}} \right. => \left \{ {{2x-2y=8} \atop {x+2y=1}} \right.[/tex]
[tex]------(+)[/tex]
[tex]3x / =9=> x=3[/tex]
[tex]x-y=4 <=>3-y=4 => y=3-4 => y=-1[/tex]
(x; y)=(3; -1) ✔
[tex]c) \left \{ {{x+2y=8} \atop {x-y=-1/*(-1)}} \right. =>\left \{ {{x+2y=8} \atop {-x+y=1}} \right.[/tex]
[tex]------(+)[/tex]
[tex]/ 3y=9 => y=3[/tex]
[tex]x-y=-1 <=> x-3=-1 => x=2[/tex]
(x; y)=(2; 3) ✔
[tex]d) \left \{ {{2x-y=9/*2} \atop {x+2y=2}} \right. => \left \{ {{4x-2y=18} \atop {x+2y=2}} \right.[/tex]
[tex]------(+)[/tex]
[tex]5x / =20 => x=4[/tex]
[tex]x+2y=2 <=> 4+2y=2 => 2y=-2 => y=-1[/tex]
(x; y)=(4; -1) ✔
[tex]e) \left \{ {{2x+y=-2/*(-2)} \atop {3x+2y=-1}} \right. =>\left \{ {{-4x-2y=4} \atop {3x+2y=-1}} \right.[/tex]
[tex]------(+)[/tex]
[tex]-x/=3 => x=-3[/tex]
[tex]3x+2y=-1 <=> -9+2y=-1 => 2y=8 => y=4[/tex]
(x; y)=(-3; 4) ✔
[tex]f) \left \{ {{4x+2y=-2} \atop {2x+3y=9/*(-2)}} \right. => \left \{ {{4x+2y=-2} \atop {-4x-6y=-18}} \right.[/tex]
[tex]------(+)[/tex]
[tex]/ -4y=-20 => y=5[/tex]
[tex]4x+2y=-2 <=>4x+10=-2 => 4x=-12 => x=-3[/tex]
(x; y)=(-3; 5) ✔
