(1)x+y/x^3-y^3 +2y/y^3-x^3
问题描述：
(1)x+y/x^3-y^3 +2y/y^3-x^3
(2)(1-4x)^2/2x+3 乘 4x^2+12x+9/4x-1
(3)x+2/x+1 - x+3/x+2 - x-4/x-3 + x-5/x-4
答
(1)x+y/x^3-y^3 +2y/y^3-x^3 =(x+y-2y)/(x^3-y^3)=(x-y)/[(x-y)(x^2+xy+y^2)]=1/(x^2+xy+y^2)(2)(1-4x)^2/2x+3 乘 4x^2+12x+9/4x-1 =(4x-1)^2/(2x+3)*(2x+3)^2/(4x-1)=(4x-1)(2x+3)(3)x+2/x+1 - x+3/x+2 - x-4/x-3 +...