名校
1 . 已知
是等差数列,
是公比不为
的等比数列,
,
,
,且
是
与
的等差中项.
(1)求
和
的通项公式.
(2)求![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d46e92ff41a3037a51bf594df6f73bc3.png)
(3)若
,证明:
.
(4)数列求和问题的关键是根据通项公式特点找到适合的求和方法,并进行合理变形,观察下列数列通项公式特点,填表:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdaa19de263700a15fcf213d64a8cd57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7def23f30138e0b7c4c1e498d6903a6c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a8ec38ab7e6912bcc97513a359bd5e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1320e2e9d9c398ec700482b06153d05b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7e82778985cd2e9f80ca7b7cabb1a85.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9632e7e5a6eb0c85cb44940c60618d67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57483e04fd1840c87ac5325157149877.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d46e92ff41a3037a51bf594df6f73bc3.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9169c81b9643e9dcd5c945d580186c97.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e06ae105393888c9e02fb2437428217c.png)
(4)数列求和问题的关键是根据通项公式特点找到适合的求和方法,并进行合理变形,观察下列数列通项公式特点,填表:
通项公式 | 求和方法名称 | 变形成可求和形式 |
![]() | ||
![]() | ||
![]() |
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2 . 在①
,
,②
,③
,
,这三个条件中任选一个,补全下列试题后并完成解答(选择多个条件并分别解答的按第1个给分)
设等差数列
的前n项和为
,且___________.
(1)求数列
的通项公式;
(2)令
,求数列
的前n项的和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f8d4c9c5b5752532b31d44a0dc0877f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5032706dd285c22e149c675da465d9ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57c599e7cec6d192fb73218e7882ceca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebfd6e425411179e2a5a06d84978356e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67431b6c84a81bab1ecb153a0ce5fe65.png)
设等差数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)令
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e0a11035037cfd4240c48bc89661374.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
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