设
是公比为
的等比数列,首项
,对于
,当且仅当
时,数列
的前
项和取得最大值,则
的取值范围为_____________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aa08a089a48737b6a0c47cd150b9f12a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daf8cadc870b9b43ab43e96aaefa1e9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fac3649308b528fd56545ba102dc42d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
更新时间:2020-01-16 13:17:29
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【推荐2】为了践行“绿水青山就是金山银山”的生态环保理念,某地计划改善生态环境,大力开展植树造林活动.该地计划每年都植树造林,若森林面积的年增长率相同,则需要5年时间使森林面积变为原来的2倍,为使森林面积变为原来的5倍以上,至少需要植树造林______ 年.(结果精确到整数,参考数据:
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解题方法
【推荐1】已知正项数列
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______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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【推荐2】记
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前
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①
;
②数列
中最大值的项是
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③公差
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④数列
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其中正确的命题是______ (填序号).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cc1f75101b6b95f198d5d469ab0934b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/390636a89883bd64bf8da9bf8654aff9.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/292e7d121918b50058fd39dd1ef18088.png)
②数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/846fa57d92d6ad44d6a0cafad1e71ed4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93bac8f65f6556af92152071a55d6533.png)
③公差
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c4ce64685821c3e55c07f151996ca8c3.png)
④数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b91adba8efbf964e9e35547b0fd0ea36.png)
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【推荐1】已知数列
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,且数列
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时,
的最大值为__ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/187fdb6607bf12dc134efbc1cd4ac72e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b399fb6f2f256feab40ac0b972a89153.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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【推荐2】已知等差数列
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