解题方法
1 . 已知数列
是公差为正数的等差数列,数列
为等比数列,且
,
,
.
(1)求数列
、
的通项公式;
(2)设数列
是由所有
的项,且
的项组成的数列,且原项数先后顺序保持不变,求数列
的前2019项的和
;
(3)对任意给定的
是否存在
使
成等差数列?若存在,用
分别表示
和
(只要写出一组即可);若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/654185eecdb28389c7994e5187671be4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccfe26b3ab1cd6a93075f24b696b0cef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/144958d8f106c2a5384404a612c35a31.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
(2)设数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ef6d44448092ebdb9e4a49d866a749.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce829c29eebf57ddc93f9127cdb1f37c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ef6d44448092ebdb9e4a49d866a749.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1adb2d553c2fa56337284d5c62adccba.png)
(3)对任意给定的
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b3743297adc123fd45565bd52ff240c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b9f65fe4c86d340d9da60c167b3256e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73a135ced51bfd0299c44abe4a6546ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1010846eeec6c9da29640f5aa3f8738.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11bc05f41215f9894e11d1df0465751a.png)
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