Question

ПОМОГИТЕ ПРОШУ!!СРОЧНО!!

Answer 1

Ответ: A a=8

                b=3

Объяснение:

$\displaystyle\\\left \{ {{ax-7y=21} \atop {5x-by=20}} \right.\ \ \ \ \ \ x=7\ \ \ \ \ \ y=5.\\\\\\\left \{ {{7a-7*5=21} \atop {5*7-5b=20}} \right.\ \ \ \ \ \ \left \{ {{7a-35=21} \atop {35-5b=20}} \right.\ \ \ \ \ \ \left \{ {{7a=56\ |:7} \atop {15=5b\ \\}:5} \right. \ \ \ \ \ \ \ \left \{ {{a=8} \atop {b=3}} \right. .$