[tex] \left \{ {{x+y+2=0} \atop {x-y-4=0}} \right. [/tex]⇔
[tex]\left \{ {{x+y=-2} \atop {x-y=4}} \right.[/tex]
Adunand membru cu membru cele doua ecuatii ale sistemului avem ca:
[tex]x+y+x-y=-2+4[/tex]⇔
[tex]2x=2[/tex]⇒[tex]x= \frac{2}{2} [/tex]⇒[tex]x=1[/tex]
[tex] \left \{ {{x+y=-2} \atop {x=1}} \right. [/tex]⇒[tex] \left \{ {{1+y=-2} \atop {x=1}} \right. [/tex]⇔[tex] \left \{ {{y=-2-1} \atop {x=1}} \right. [/tex]⇒[tex]y=-3[/tex]
Solutia sitemului este:
[tex]S=\{1, -3\}[/tex]
