Question

Решить систему уравнений:
In x - In y = In3
x-2y=5

Answer 1

$left { {{lnx - lny = ln3} atop {x - 2y = 5}} right. left { {{ln frac{x}{y} = ln3} atop {x=5 + 2y}} right. left { {{ frac{x}{y}=3} atop {x=5+2y}} right.$

Заменяем 

$frac{5 +2y}{y} =3$

$frac{5+2y}{y} - frac{3y}{y} = 0$

$frac{5+2y-3y}{y} = 0$

5 - y =0
- y = - 5
y = 5

x = 5 + 2y
x = 5 + 10
x = 15

Ответ: (15;5)