....求名高手帮莪做以下题目.. xyz=1 求xy+x+1分子x+yz+y+1分子y+zx+z+1分子Z

是x/(xy+x+1) + y/(yz+y+1) + z/(xz+z+1)吧
先看x/(xy+x+1),因为xyz=1 ,带入其中的1,可得:
x/(xy+x+1)=1/(y+1+yz)
再看z/(xz+z+1),把xz=1/y带入可得:
z/(xz+z+1)=zy/(y+1+yz)
这样三者分母相同了,可以合并了,结果为:
x/(xy+x+1) + y/(yz+y+1) + z/(xz+z+1)
=1/(y+1+yz)+y/(yz+y+1)+zy/(y+1+yz)
=1

清楚些的:
x/(xy+x+1)+y/(yz+y+1)+z/(xz+z+1)
=x/(xy+x+xyz)+y/(yz+y+1)+z/(xz+z+1)
=1/(y+1+yz)+y/(yz+y+1)+z/(xz+z+1)
=(1+y)/(y+1+yz)+z/(xz+z+1)
=(1+y)/(y+1+yz)+zy/(yxz+yz+y)
=(1+y)/(y+1+yz)+zy/(1+yz+y)
=(1+y+yz)/(y+1+yz)
=1