Question

решите систему уравнений

Answer 1

$\left \{ {{a+b=4} \atop {3a-5b=20}} \right. \\\\\left \{ {{b=4-a} \atop {3a=20+5b}} \right. \\\\\left \{ {{b=4-a} \atop {3a=20+5(4-a)}} \right.\\\\\left \{ {{b=4-a} \atop {3a=40-5a}} \right.\\\\\left \{ {{b=4-a} \atop {8a=40}} \right.\\\\\left \{ {{b=4-a} \atop {a=5}} \right.\\\\\left \{ {{a=5} \atop {b=-1}} \right.$

Ответ:

a=5

b=(-1)