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解题方法
1 . 已知正项数列
的前n项和为
,且
是4和
的等比中项,数列
,其前n项的和为
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fbfc875ca919921e8f63a6fca648561b.png)
__________ ,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79a8462c07c0143853c1bec52084360e.png)
__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23016d1186ebefd8d67387f43f100229.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e722d1cb06e597485399a64c75b14a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fbfc875ca919921e8f63a6fca648561b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79a8462c07c0143853c1bec52084360e.png)
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2020-07-20更新
|
638次组卷
|
2卷引用:四川省遂宁市船山区第二中学校2020届高三高考适应(二)考试数学(文)试卷
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2 . 已知
是数列
的前
项和,对任意
,都有
;
(1)若
,求证:数列
是等差数列,并求此时数列
的通项公式;
(2)若
,求证:数列
是等比数列,并求此时数列
的通项公式;
(3)设
,若
,求实数
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cea4ac187cbb465180e89f38250b3970.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4faa5d8f3b8d5f59910ef3e885abe4fc.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/711b21672fd907c5c92fee1d649e7003.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/46db680bc60929939e0f09990c03583e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ac5c639aa5cd63ab86b2b0d9a23c998.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6788d3dbbd2d5f865db8d414375339e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(3)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d8ba3d72887756e8d222e0e3ae6aff5b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/75330ac9e51cdef4bc61012551e1d00b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
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2019-12-08更新
|
766次组卷
|
3卷引用:2018年上海市复旦附中高三5月三模数学试题
3 . 已知数列
与
满足
,
.
(1)若
,求数列
的通项公式;
(2)若
,且数列
是公比等于2的等比数列,求
的值,使数列
也是等比数列;
(3)若
,且
,数列
有最大值
与最小值
,求
的取值范围.
![](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/998926638c7b8a50714455fb2c81693b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36b98ef143f8159f3a7dafa1fd2f2370.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10226aabc54614cdc01a68b1a60a5770.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/078a5f2f480f345ecc5a13bd09ce539f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07d96beb63c117094ca155b15c72ac28.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de524a163912682710d2a1918d66ff40.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/467f61f8d38c71fcb30f3f16d88650d7.png)
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2020-02-08更新
|
429次组卷
|
2卷引用:2016届上海市崇明县高三第二次高考模拟(文)数学试题
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4 . 设满足以下两个条件的有穷数列
为
阶“期待数列”:①
;②
.
(1)若等比数列
为
阶“期待数列”
,求公比
;
(2)若一个等差数列
既是
阶“期待数列”又是递增数列
,求该数列的通项公式;
(3)记
阶“期待数列”
的前
项和为
,求证;数列
不能为
阶“期待数列”.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d02a8555da4dbbc7820a50a95b071ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/afa0fca4198a6d5c5b76e5e1716dc4e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/39aa494487b73dbac3d6b868d822fddd.png)
(1)若等比数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5631bc01b998a4b3fabd9e131699dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1306375a0fec4eb4bf3f07992f6716e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
(2)若一个等差数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5631bc01b998a4b3fabd9e131699dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1306375a0fec4eb4bf3f07992f6716e.png)
(3)记
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/45581140d4687ff796b7cc53609702e6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ea210b22ee669a90173c4bd61c39596.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/500c42aa6116832f6ef1fe41d3d214bc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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