若x,y,z∈R,且x+y+z=xyz,

设1／x＝p1／y＝q1／z＝r则pq+qr+pr=1(y+x)/z+(y+z)/x+(z+x)/y≥2(1/x+1/y+1/z)^2为(pq+qr+pr)[r/p+r/q+q/r+q/p+p/r+p/q]>=2(p+q+r)^2即2(r^2+p^2+q^2+pq+qr+rp)+rrq/p+rrp/q+qqr/p+qqp/r+ppr/q+ppq/r>=2(p+q+r)^2即...