解题方法
1 . 给出下列5个命题:
①在等差数列
中,若
,其中m,n,p,q均为正整数,则一定有
.
②任意两个实数a,c的等比中项为
;
③若等比数列
的公比
,则其前n项和
;
④数列
的通项公式是
,且
,则
.
⑤等差数列
中,前n项和
,有最小值,则公差
;
其中正确命题的序号为( )
①在等差数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/095397b70a73758437ba2198b61fd79b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fb679318d0c9819b82e51a1750b502a.png)
②任意两个实数a,c的等比中项为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/169b55e4b8203bc7fa3597229de648ec.png)
③若等比数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/45482d31d1d7448c9f3922b4d2a55331.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7653925d3f05c893cfe08c7c22f3751.png)
④数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b39bacf2989caafaba2ed8d36171f912.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a90eb772927e69564d3ae98f716fa4ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c88248a34d270530f9d01570a911878.png)
⑤等差数列
![](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/4f8e68eb4ade6e22982d2df5102d8894.png)
其中正确命题的序号为( )
A.②④ | B.③⑤ | C.①⑤ | D.③④⑤ |
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