已知数列
是公差为2的等差数列,若
成等比数列,则
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dff57fdacecdec5b0289f7b75f17403.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6bc0cd1b5a528a5719a29a6fa6996281.png)
A.9 | B.12 | C.18 | D.27 |
更新时间:2024-05-16 10:28:26
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【推荐1】已知等差数列
的前
项积为
,若
,则当
取得最小值时,
的值为( )
![](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/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/face2a7ed4717f422331f6c78a0ea2f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
A.5 | B.6 | C.7 | D.8 |
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【推荐2】《九章算术》是我国古代内容极为丰富的数学名著,书中有如下问题:“今有垣厚五尺,两鼠对穿.大鼠日一尺,小鼠亦日一尺.大鼠日自倍,小鼠日自半.问几何日相逢?各穿几何?”,翻译成今天的话是:一只大鼠和一只小鼠分别从的墙两侧面对面打洞,已知第一天两鼠都打了一尺长的洞,以后大鼠每天打的洞长是前一天的2倍,小鼠每天打的洞长是前一天的一半,已知墙厚五尺,问两鼠几天后相见?相见时各打了几尺长的洞?设两鼠x 天后相遇(假设两鼠每天的速度是匀速的),则x=( )
A.![]() | B.![]() | C.![]() | D.![]() |
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【推荐1】正项等比数列
中,
是
与
的等差中项,若
,则
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73f6aba03136f0c6d7c4de8f2a6e63b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f65fc200f10b97588a0c9896277c9c64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8c001508aa9f2c46e55dfd1c4d99d34d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4123422b5a6621da6a3214aa8c3e2a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3e3cd7b1cb03860f90838500d905eea.png)
A.4 | B.8 | C.32 | D.64 |
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【推荐2】设
是首项为
,公差为-1的等差数列,
为其前n项和,若
成等比数列,则
=( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f8aa010f7105f3ca426c8a34880abd2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
A.2 | B.-2 | C.![]() | D.![]() |
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