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[函数] 一个函数不等式问题

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力工 Posted 2019-6-9 15:38 |Read mode
Last edited by 力工 2019-6-9 19:11已知函数$f(x)=1+x^2-4xlnx$的一个零点$m(1<m<e)$,求证:对任意的
$x:0<x<m$都有$x\sqrt{f(x)}+[x-2(lnx+1)]\sqrt{1+x^2}\leqslant 0$.

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realnumber Posted 2019-6-9 17:11
几何画板画了下图,发现有两个零点约1.8,8.4,没有(0,1)内零点,又题目好丑,原始问题是什么?

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kuing Posted 2019-6-9 17:27
回复 2# realnumber

简直是丑得掉渣……

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 Author| 力工 Posted 2019-6-9 19:09
正是丑才没法下口。找不到变形下口的地方,硬算也难
朱老师说得对,这货$m$应该是$1<m<e$.

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