Question

$left { {{xy=18} atop {2x+y=15}} right.$

Answer 1

2x + y = 15, 2xy = 36

По теореме, обратной теореме Виета, 2x и y - решения квадратного уравнения
t^2 - 15t + 36 = 0
t1 = 3, t2 = 12

1) 2x = 3, y = 12
x = 3/2, y = 12
2) 2x = 12, y = 3
x = 6, y = 3