Question

X+2Y=5 -X+Y=1 ________________________________________________________________x+y=-1 2X-Y=7

Answer 1

$1)\; \; \left \{ {{x+2y=5} \atop {-x+y=1}} \right. \oplus \left \{ {{3y=6} \atop {x=y-1}} \right. \; \left \{ {{y=2} \atop {x=1}} \right. \; \; \to \; \; (1,2)\\\\2)\; \; \left \{ {{x+y=-1} \atop {2x-y=7}} \right. \oplus \left \{ {{3x=6} \atop {y=2x-7}} \right. \; \left \{ {{x=2} \atop {y=-3}} \right. \; \; \to \; \; (2,-3)$