(y+z)/x=y/x+z/x≥2(√yz)/x同理可得(y+z)/x+(x+z)/y+(x+y/z)≥2*[(√yz)/x+(√xz)/y+(√xy)/z]由x+y+z=xyz得(x+y)/z+1=xy≥1同理yz,xz≥1所以(y+z)/x+(x+z)/y+(x+y/z)≥2(1/x+1/y+1/z)
