1 . 已知等差数列{
}的首项为a
.设数列的前n项和为Sn,且对任意正整数n都有
.
(1)求数列{
}的通项公式及Sn;
(2)是否存在正整数n和k,使得
成等比数列?若存在,求出n和k的值;若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88c8c4c2c1841dc214d272006a57d1d1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e04d4139bce0da390d0134f92aa0f4cc.png)
(1)求数列{
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
(2)是否存在正整数n和k,使得
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0183f8b4052ab7d8449870388f26b619.png)
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2016-12-02更新
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2卷引用:2013-2014学年湖北武汉蔡甸区第二中学高一下六科竞赛理科数学试卷