Forgot password?
 Register account
View 254|Reply 1

[数列] 数列的max问题

[Copy link]

107

Threads

225

Posts

2905

Credits

Credits
2905

Show all posts

facebooker Posted 2024-5-23 15:08 |Read mode
Last edited by facebooker 2024-5-23 19:27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。

413

Threads

1431

Posts

110K

Credits

Credits
11100

Show all posts

realnumber Posted 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.

Mobile version|Discuz Math Forum

2025-5-31 11:14 GMT+8

Powered by Discuz!

× Quick Reply To Top Edit