3x + y = - 1
x - xy = 8
y = - 1 - 3x
x - x ( - 1 - 3x) = 8 *
* Решим вспомогательное уравнение
x + x + 3x^2 - 8 = 0
3x^2 + 2x - 8 = 0
D = 4 + 96 = 100 = 10^2
x1 = ( - 2 + 10)/6 = 8/6 = 4/3
x2 = ( - 2 - 10)/6 = - 12/6 = - 2;
x1 = 4/3
y1 = - 1 - 3*(4/3) = - 1 - 4 = - 5;
x2 = - 2
y2 = - 1 + 3*2 = 5
Ответ:
( 4/3; - 5); ( - 2; 5)