已知x\5=y\3,求(x\x+y)+(y\x-y)-(y^2\x^2-y^2)的值_数学解答

已知x\5=y\3,求(x\x+y)+(y\x-y)-(y^2\x^2-y^2)的值

人气：362 ℃　时间：2020-05-13 08:05:29

解答

x/5=y/3,则x=5y/3x/(x+y) + y/(x-y) - y^2/(x^2-y^2)= [x(x-y)+ y(x+y) -y^2] / (x^2-y^2)= x^2 /(x^2-y^2)=(5y/3)^2/ [(5y/3)^2-y^2]= (25/9)/(25/9 - 1)=25/(25 - 9)=25/16