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.
(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
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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