4x^3-4x^2y-(x-y)=4x²(x-y)-(x-y)=(x-y)（4x²-1）=(x-y)(2x+1)(2x-1)
4x^3-4x^2y-(x-y)=4x^2(x-y)-(x-y)=(x-y)(4x^2-1)=(x-y)(2x-1)(2x+1)
