已知
是等比数列,若
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62ffbfb2502cc0ef8c5e1e60c567df35.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f86a8746a583f411fb73c6334eb27b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/170b74434f9726be33895bbd3bfec4f4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62ffbfb2502cc0ef8c5e1e60c567df35.png)
更新时间:2022-09-07 17:51:58
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【知识点】 等比中项的应用
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【推荐1】等差数列{an}的公差为﹣2,且a1,a3,a4成等比数列,则a20=_____ .
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