Question

Решить систему тремя способами:
1)Постановки;
2)Сложения;
3)Графический.
{{x+2y=18}}
{{-x+3y=2}}

Answer 1

$1)\; \; \left \{ {{x+2y=18} \atop {-x+3y=2}} \right. \; \left \{ {{3y-2+2y=18} \atop {x=3y-2}} \right. \; \left \{ {{5y=20} \atop {x=3y-2}} \right. \; \left \{ {{y=4} \atop {x=3\cdot 4-2}} \right. \; \left \{ {{y=4} \atop {x=10}} \right. \\\\2)\; \; \left \{ {{x+2y=18} \atop {-x+3y=2}} \right. \oplus \left \{ {{5y=20} \atop {-x+3y=2}} \right. \; \left \{ {{y=4} \atop {-x+12=2}} \right. \; \left \{ {{y=4} \atop {-x=-10}} \right. \; \left \{ {{y=4} \atop {x=10}} \right. \\\\3)$