Решите систему уравнений х^2+y^2=9 xy=2

X^2+(2/x)^2-9=0; xy=2
x^2+(4/x^2)-9=0; xy=2
x^4+4-9x^2=0; xy=2
x^4-9x^2+4=0; xy=2
D=81-16=65
x^2=(9+8,06)/2=0,47; x^2=(9-8,06)/2=6.04
x=-0.68 y=-2.94
x=0.68  y=2.94
x=-2.94 y=-0.68
x=2.94 y=0.68