[tex] \left \{ {{a+b = -404} \atop {a-b = 186}} \right. =\ \textgreater \ \left \{ {{a = -404-b} \atop {-404-b-b = 186}} \right.=\ \textgreater \ \left \{ {{a = -404-b} \atop {-404-2b = 186}} \right. =\ \textgreater \ \left \{ {{a = -404-b} \atop {-2b = 186+404}} \right. [/tex][tex] \left \{ {{a = -404-b} \atop {-2b = 590}} \right.=\ \textgreater \ \left \{ {{a = -404-b} \atop {b = 590/-2}} \right.=\ \textgreater \ \left \{ {{a = -404-b} \atop {b = -295}} \right.=\ \textgreater \ \left \{ {{a = -404+295} \atop {b = -295}} \right.=\ \textgreater \ [/tex][tex] \left \{ {{a = -109} \atop {b = -295}} \right. [/tex]
Verificam : a+b = -404 ⇒-109+(-295) = -109-295 = -404
a-b = 184 ⇒-109-(-295) = -109+295 = 186
semnul acesta "=>" intre sistem este echivalent
