a)[tex] \left \{ {{x+y=10} \atop {2x-y=-1}} \right.[/tex]
Inmultim prima relatie cu 2. Obtinem: [tex] \left \{ {{2x+2y=20} \atop {2x-y=-1}} \right. [/tex].
Scadem relatiile si obtinem: 3y=21 => y=7.
x+y=10 => x=10-y=10-7=3.
b)[tex] \left \{ {{y-2x=1} \atop {6x-y=7}} \right. [/tex]
Adunam relatiile si obtinem 4x=8 => x=2.
y-2x=1 =>y=1+2x=1+4=5
c)[tex] \left \{ {{x-y=2} \atop {-2x+y=-4}} \right. [/tex]
Adunam relatiile si obtinem: -x=-2=>x=2.
x-y=2 => y=x-2=2-2=0
d)[tex] \left \{ {{3x+y=4} \atop {6x+2y=1}} \right. [/tex]
Inmultim prima realtie cu 2 si obtinem:
[tex] \left \{ {{6x+2y=8} \atop {6x+2y=1}} \right. [/tex]. Acest sistem nu are solutii.
