Răspuns:
(x,y)apartine{(2, -1);(-1, 2)}
Explicație pas cu pas:
x + 3xy + y = -5
x + 3 * -2 + y = - 5
x + (-6) + y = - 5
x + y = 1
x = 1 - y
(1-y)* y = -2
y - y * y = -2
- y* y + y + 2 = 0
y la 2 - y - 2 = 0
y la 2 + y - 2y - 2 = 0
y(y + 1) - 2(y + 1) = 0
(y + 1)(y-2) = 0 => y + 1 = 0 => y = -1 => x = 2
y - 2 = 0 => y = 2 => x = -1
