题目内容
已知数列{bn}的前n项和
．数列{an}满足
，数列{cn}满足
．
（1）求数列{an}和数列{bn}的通项公式；
（2）若
对一切正整数n恒成立，求实数m的取值范围．
．数列{an}满足，数列{cn}满足．（1）求数列{an}和数列{bn}的通项公式；
（2）若
对一切正整数n恒成立，求实数m的取值范围．19．(1) 当
时，
······ 2分
又
适合上式
∴
···································································· 3分
由
·························································· 5分
(2)
···································································· 6分
∵
∴
，即
∴ {cn}的最大项为
··································································· 9分
∴
∴
∴实数m的取值范围为················································ 12分
时，······ 2分又
适合上式∴
···································································· 3分由
·························································· 5分(2)
···································································· 6分∵
∴
，即∴ {cn}的最大项为
··································································· 9分∴
∴
∴实数m的取值范围为
················································ 12分略
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