多盈理财下载:解分式题

来源:百度文库 编辑:高校问答 时间:2024/04/30 21:25:25
请教:
若x+y+z≠0,且x/(y+z)=a,y/(x+z)=b,z/(x+y)=c,求证a/(1+a)+b(1+b)+c(1+c)=1

解:1+a=1+x/(y+z)=(x+y+z)/(y+z)
1+b=1+y/(x+z)=(x+y+z)/(x+z)
1+c=1+z/(y+x)=(x+y+z)/(y+x)
a/(1+a)=x/(x+y+z)
b/(1+b)=y/(x+y+z)
c/(1+c)=z/(x+y+z)
∴a/(1+a)+b(1+b)+c(1+c)
=x/(x+y+z)+y/(x+y+z)+z/(x+y+z)
=(x+y+z)/(x+y+z)
=1