xy-6=0⇒x=6/y
x^2+y^2=36/(y^2)+y^2=20
36+y^4=20y^2
обозначим t=y^2, тогда t^2-20t+36=0
D = b^2 - 4 * a * c = (-20)^2 - 4 * (1) * (36) = 256
t1 = (-b + sqrt(D)) / (2*a)
=18
t2 = (-b - sqrt(D)) / (2*a)=2
y=√t
y1=√2 x1=3√2
y2=-√2 x1=-3√2
y3=3√2 x3=√2
y4=-3√2 x4=-√2