若x=2012,y=2013,则(x+y)×[(x^2+y^2)/x^4-y^4)]_数学解答

若x=2012,y=2013,则(x+y)×[(x^2+y^2)/x^4-y^4)]

人气：275 ℃　时间：2020-05-12 09:05:05

解答

(x+y)×[(x^2+y^2)/(x^4-y^4)]
=(x+y)×[(x^2+y^2)/(x^2+y^2)(x^2-y^2)]
=(x+y)×[1/(x+y)(x-y)]
=1/(x-y)
=1/(2012-2013)
=-1