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[数列] 数列的max问题

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facebooker Post time 2024-5-23 15:08 |Read mode
本帖最后由 facebooker 于 2024-5-23 19:27 编辑 设$0\leqslant a_1<a_2<\cdots <a_{99}<a_{100}\leqslant 1, a_{n+1}\geqslant 3a_n,(1\leqslant n\leqslant 99), $若$\max\left\{a_{n+1}-a_{n}\right\}\ge m$恒成立,求$m$的取值范围。

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realnumber Post time 2024-5-26 07:42
那就取$a_{100=1},a_1=0$,依次$a_{n+1}= 3a_n$填满长度为1的区间,这样是首项是$a_2-a_1=b$.公比为3,末项为$a_{100}-a_{99}=c$.共99项的等比数列,
此时$\frac{b(1-3^{99})}{1-3}=1,m\le b3^{98}$,解答题,"="改成"$\le$"包括等比数列.

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