y-2x=0,求代数式(x^2-y^2)(x^2-xy+y^2)/(x+Y)(x^3-y^3)的值

y-2x=0,求代数式(x^2-y^2)(x^2-xy+y^2)/(x+Y)(x^3-y^3)的值

y=2x带入后面式子
(x^2-4x^2)(x^2-2x^2+4x^2)/(3x)(x^3-8x^3)=-9x^4/-21x^4=3/7