化简,求值(x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2)-2.其中x=2+√5,y=2-√5_数学解答

化简,求值(x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2)-2.其中x=2+√5,y=2-√5

人气：279 ℃　时间：2020-05-19 01:38:48

解答

(x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2)-2
=(x-y/x+2y)/[(x-y)(x+y)/(x+2y)^2]-2
=(x+2y)/(x+y)-2
=-x/(x+y)
=-(2+√5)/4