xyz=1所以z=1/xyxz=1/yyz=1/xx/(xy+x+1)+y/(yz+y+1)+z/(xz+z+1)=x/(xy+x+1)+y/(1/x+y+1)+(1/xy)/(1/y+1/xy+1)第二个分子分母同乘以x第三个分子分母同乘以xy=x/(xy+x+1)+xy/(xy+x+1)+1/(xy+x+1)=(xy+x+1)/(xy+x+1)=1
