y-2x=0
y=2x
(x^2-y^2)(x^2-xy+y^2)/(x^2+xy+y^2)(x^2-y^2).
=(x^2-xy+y^2)/(x^2+xy+y^2)
=(x^2-2x^2+4x^2)/(x^2+2x^2+4x^2)
=3x^2/7x^2
=3/7
y-2x=0
y=2x
(x^2-y^2)(x^2-xy+y^2)/(x^2+xy+y^2)(x^2-y^2).
=(x^2-xy+y^2)/(x^2+xy+y^2)
=(x^2-2x^2+4x^2)/(x^2+2x^2+4x^2)
=3x^2/7x^2
=3/7