Решите уравнения( сложением и подстановкой)

1)
$\left \{ {{ \frac{x+y-xy}{xy(x+y)} = \frac{1}{2} } \atop {xy(x+y)=2}} \right. \\ \left \{ {{ x+y-xy = 1} \atop {xy(x+y)=2}} \right.\\ \left \{ {{ (x-1)(1-y)=0 } \atop {xy(x+y)=2}} \right.\\$

1) x = 1
y(1+y)=2
y² + y - 2 = 0
D = 1 + 8 = 9
y₁ = (-1-3)/2=-2
y₂ = (-1+3)/2=1

Ответ: (-2; 1); (1; -2); (1; 1)

2) $\left \{ {{x(1+y)=3} \atop {xy^2(1+y)=12}} \right. \\ \left \{ {{x(1+y)=3} \atop {3y^2=12}} \right. \\$

y²= 4
y₁ = -2
y₂ = 2

x₁(1-2)=3
x₁ = -3

x₂(1+2)=3
x₂ = 1

Ответ: (-3; -2); (1; 2)