题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230531-73791.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230532-26894.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230532-33945.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230532-22056.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230533-67561.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230531-73791.png)
( )
A.![]() | B.![]() | C.![]() | D.![]() |
答案
解析
专题:计算题.
分析:先根据a4-a2=4求得公差d,进而根据等差数列的求和公式和S3=9求得a1,最后根据等差数列的通项公式求得答案.
解答:解:设数列的公差为d,依题意可得
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230534-19839.png)
∴an=1+(n-1)×2=2n-1
故选C
点评:本题主要考查了数列的通项公式.解题的关键是熟练掌握等差数列的通项公式和求和公式.
核心考点
举一反三
已知数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230520-84877.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230520-78917.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230520-71122.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230521-93170.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230521-28053.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230521-91559.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230521-73055.gif)
(Ⅰ)求证:数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230522-18729.gif)
(Ⅱ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230521-91559.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230522-21065.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230522-32830.gif)
(Ⅲ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230522-42866.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230522-21065.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230523-41098.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230507-17640.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230508-78045.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230508-77787.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230430-24311.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230431-81831.gif)
(Ⅰ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230431-62090.gif)
(Ⅱ)证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230431-23564.gif)
(Ⅲ)在点列An(2n,
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230431-69195.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230432-45216.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230432-51485.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230432-76740.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230412-48789.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230412-66663.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230412-67144.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230413-60027.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230413-25745.gif)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230412-48789.gif)
(2)设数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230413-36459.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230412-67144.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230413-93809.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230414-81718.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230414-52273.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230414-34385.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230414-75566.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230405-35426.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230406-96220.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230406-65259.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230406-34456.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012230406-96220.gif)
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