已知x=(b+c)分之a,y=(c+a)分之b,z=(a+b)分之c,求:(1+x)分之x+(1+y)分之y+(1+z)

1+x=1+a/(b+c)=（a+b+c)/(b+c)
x/(1+x)=[a/(b+c)]/[(a+b+c)/(b+c)]=a/(a+b+c)
同理：
y/(1+y)=b/(a+b+c)
z/(1+z)=c/(a+b+c)
(1+x)分之x+(1+y)分之y+(1+z)分之z
=a/(a+b+c)+b/(a+b+c)+c/(a+b+c)
=（a+b+c)/(a+b+c)
=1