求(x2-xy+y2)/(x2+xy+y2)的极值,x>0 y>0
问题描述:
求(x2-xy+y2)/(x2+xy+y2)的极值,x>0 y>0
答
x2+y2>=2xy
(x2-xy+y2)/(x2+xy+y2)
=1-2xy/(x2+xy+y2)
=1/3
(x2-xy+y2)/(x2+xy+y2)