Разделить 2 уравнение на y^3
(x/y)^3+2(x/y)^2-(x/y)-2=0
x/y=t
t^3+2t^2-t-2=0
t^2(t+2)-(t+2)=0
(t^2-1)(t+2)=0
(t-1)(t+1)(t+2)=0
t=1; -1; -2
1) x^2+y^2=8
x/y=1
x=y
2y^2=8
y^2=4
y1=2
y2=-2
x1=2
x2=-2
2) x^2+y^2=8
x/y=-1
x=-y
y^2=4
y3=2
y4=-2
x3=-2
x4=2
3) x^2+y^2=8
x/y=2
x=-2y
4y^2+y^2=8
y^2=8/5
y5=sqrt(8/5)
y6=-sqrt(8/5)
x5=-2sqrt(8/5)
x6=2sqrt(8/5)
Ответ: (+-2;+-2), (2sqrt(8/5);-sqrt(8/5)), (-2sqrt(8/5);sqrt(8/5))