m+n=6.求(4m+n)/mn的最小值
问题描述：
m+n=6.求(4m+n)/mn的最小值
答
(4m+n)/mn
=4/n+1/m
=1/n+1/n+1/n+1/n+1/(2m)+1/(2m)
基本不等式,6/(1/a+1/b+1/c+1/d+1/e+1/f)=36/(4m+4n)=3/2
等号成立时,n=2m,n=4,m=2时最小值3/2