设(空谈y+z)/吵宴(x)=(z+x)/(y)=(x+y)/(升亏银z)=k,其中k≠0那么:y+z=kx,z+x=ky,x+y=kz所以:y+z+z+x+x+y=k(x+y+z)即:2(x+y+z)=k(x+y+z)因为x+y+z≠0,所以解得:k=2那么:x+y=2z所以:(x+y-z)/(x+y+z)=(2z-z)/(2z+z)=z/(3z)=1/3