求解学霸
2014-11-12
展开全部
(1)王强 10x+10y 元 李刚10/x + 10/y 支
(2)M = (10x + 10y)/20 = (x+y)/2
N = 20/(10/x + 10/y) = 2xy/(x+y)
(3) M/N = (x+y)^2/4xy = [(x-y)^2 + 4xy]/4xy >= 4xy/4xy = 1
当x = y时是一样的
当x !=y时,M值要大,所以第二种方法划算
(2)M = (10x + 10y)/20 = (x+y)/2
N = 20/(10/x + 10/y) = 2xy/(x+y)
(3) M/N = (x+y)^2/4xy = [(x-y)^2 + 4xy]/4xy >= 4xy/4xy = 1
当x = y时是一样的
当x !=y时,M值要大,所以第二种方法划算
追答
求采纳哦 谢谢亲啦
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