1 . 在正项等比数列
中,
为其前
项和,若
,
,则
的值为______ .
![](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/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e3931e6266decbab4ab76b280f61bda.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b60c92966388420d68570cd838a242ce.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/973d17cd50a4905164d29b8449fafd52.png)
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解题方法
2 . 已知等差数列
满足
,
为其前
项和,若
,
,则
的最大值为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4927f5e4c0004453b4071074b543fa71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10599e638e83e2b43b08315a7ba93517.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/655c46b33730f3a29b9ec3024df71375.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
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3 . 在等差数列
中,
为其前
项的和,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3bc625e19e7ca2b9d097f67a3d472e47.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/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c416a7f59513cdc00111e3b1ddcfea60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3bc625e19e7ca2b9d097f67a3d472e47.png)
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4 .
表示不小于x的最小整数,例如
,
.已知等差数列
的前n项和为
,且
,
.记
,则数列
的前10项的和______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7aa5efc9350c3ad41f456d434564f82e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25c314bd3e07c88abd2931344a30d11a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/739718565082441c3e1a9b3e22e1735f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6760775a38ed18ab8f346346e25de2ec.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac51814852f7070293f0e7ddcf4a0691.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b2dbf1896e958f7b0b715be6ab1b799.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
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5 . 已知等差数列
的前n项和为
,若
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dbd9ff686703cad03aa383e5fec21.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/2693734765399876e9e93cdb110231c4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/185eb7967e13ada069ff64a009b07503.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dbd9ff686703cad03aa383e5fec21.png)
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解题方法
6 . 记公差不为0的等差数列
的前n项和为
,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dd707b69a11f8de5566f23c1a2a9ff5a.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/af8cda87e605e17e862cb21b0e23d0f4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dd707b69a11f8de5566f23c1a2a9ff5a.png)
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7 . 设为
等差数列
的前n项和,已知
、
、
成等比数列,
,当
取得最大值时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f3cb8d72bb2e281b943b3b430138ef7.png)
______ .
![](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/e097c8d4c948de063796bd19f85b3a9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e0bd63f55069a3bc870915010b39225.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f30f56664446f32dbbc2c5f12a99374.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87d85252ec30a427151f300503e3024d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2297a9ddfd3d681025c3dc5a93d6751f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f3cb8d72bb2e281b943b3b430138ef7.png)
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8 . 已知数列
是等差数列,其公差为d,前n项和为
,若
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c98c59cd4749afdd21e73529fc84323.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/2693734765399876e9e93cdb110231c4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d7f67e6f9f75fe5e80873eac20abc83b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c98c59cd4749afdd21e73529fc84323.png)
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9 . 已知数列
的通项公式为:
,其前
项和为
,若
成等比数列, 则 k=___________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/677e46ecd051c92489c0d1d458932f37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/183029f2aef88fac0a62daa4e02972e2.png)
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解题方法
10 . 已知等差数列
的前
项和为
,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/530147419685f6091bf25a0b3e2662ab.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/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7cfb2cd804cdcb5acb9d129b66c281d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/530147419685f6091bf25a0b3e2662ab.png)
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