xyz=1
得x=1/yz
xy=1/z
xz=1/y
x/xy+x+1+y/yz+y+1+z/xz+z+1
=(x/xy+x+1)+(y/yz+y+1)+(z/xz+z+1)
=(1/yz)/(1/z+1/yz+1)+y/(yz+y+1)+z/(1/y+z+1)
=1/(yz+y+1)+y/(yz+y+1)+yz/(yz+y+1)
=(yz+y+1)/(yz+y+1)
=1
9
9,假设x=y=z=1,
原式=x/(xy+x+xyz)+y/(yz+y+1)+z/(xz+z+1)
=1/(y+1+yz)+y/(yz+y+1)+yz/(yxz+yz+y)
=(1+y)/(yz+y+1)+yz/(1+yz+y)
=(1+y+yz)/(1+y+yz)
=1
如果不要过程的话假设x=1,y=1,z=1.就是取特殊值。带入。得到9.
要是简答题。。。我还没想出来。。