已知等差数列{an}中,a2 =3,a5=9.
(1)求{an}的通项公式;
(2)令bn =2an,求数列{bn} 的前n项和Sn;
(3)令
,求数列{cn)的前n项和Tn.
(1)求{an}的通项公式;
(2)令bn =2an,求数列{bn} 的前n项和Sn;
(3)令
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abb9c16c307a54e119f68392903cac66.png)
更新时间:2021-08-27 11:48:19
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