Question

Решите систему уравнение способом сложения:
a+b=4,
2a+7b=2;

Answer 1

$left { {{a+b=4, |cdot (-2)} atop {2a+7b=2}} right. ; left { {{-2a-2b=-8} atop {2a+7b=2}} right. ; oplus left { {{5b=-6} atop {a+b=4}} right. ; left { {{b=-1,2} atop {a=4-b}} right. \\ left { {{b=-1,2} atop {a=5,2}} right.$

Answer 2

-2a-2b=-8
2a+7b=2
5b=-6
b=-6/5