已知x=2003,y=2004,则(x+y)*(x^2+y^2)/(x^4-y^4)=
问题描述：
已知x=2003,y=2004,则(x+y)*(x^2+y^2)/(x^4-y^4)=
答
(x+y)*(x^2+y^2)/(x^4-y^4)
=(x+y)(x^2+y^2)/[(x^2+y^2)(x+y)(x-y)]
=1/(x-y)
=1/(2003-2004)
=-1