证明：∵x+y+z=1∵1/x+1/y+1/z=1=1/（x+y+z)∴(x+y+z)(1/x+1/y+1/z)=1∴(x+y+z)(yz+zx+xy)-xyz=0∴(x+y+z)[y(x+z)+zx(x+y+z)]-xyz=0∴(x+y+z)y(x+z)+zx(x+z)=0∴(x+z)(xy+y^2+yz+xz)=0∴(x+z)(x+y)(y+z)=0∴(1-y)(1-...