已知△ABC的三边长a,b,c成等差数列,且a2+b2+c2=63,则实数b的取值范围是( )
A.[3![]() ![]() | B.(3![]() ![]() | C.[2![]() ![]() | D.(2![]() ![]() |
更新时间:2020-03-18 09:00:43
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【知识点】 等差中项的应用
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解题方法
【推荐1】等差数列
中,
是函数
的极值点,则
的值是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79d0df8d8dde2e820e759cc3e37b934d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de712b9e0375eeb81a46af37aa0fee6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/093147d6fd28313261b49b9affb5af11.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
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单选题
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较易
(0.85)
【推荐2】各项都是正数的等比数列
的公比
,且
,
,
成等差数列,则
的值为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29518f13a1ebc3fff8181c2d7cfba22f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/369c7e3138987c4b997d86e6777df930.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cb5ca241bb7c313ef0366d3ddba93bc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20071a42c1f9eac2b173d77d37381da9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b42791b77924729f7e31712177b26af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f93e44372301b5b889d285ce478b143.png)
A.![]() | B.![]() | C.![]() | D.![]() ![]() |
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