1 /(x-y)—1/(x+y)+ 2y/(x^2+y^2)—4x^2y/(x^4+y^4)
={1 /(x-y)—1/(x+y)++ 2y/(x^2+y^2)—4x^2y/(x^4+y^4)
=2y/(x^2-y^2)+ 2y/(x^2+y^2)—4x^2y/(x^4+y^4)
={2y/(x^2-y^2)+ 2y/(x^2+y^2)}—4x^2y/(x^4+y^4)
=4x^2y/(x^4-y^4)-4x^2y/(x^4+y^4)
=4x^6y/(x^8-y^8)
这题一看似乎有些麻烦,因为直接把四项分母化成统一挺麻烦的,但是计算时可以每两项加一次然后这么算几次,每次都是把两项分母化成统一,这样少简单些