题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080905-58642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080905-11509.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080906-43444.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080906-95768.png)
(Ⅰ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080905-58642.png)
(Ⅱ)记
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080906-27671.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080906-16268.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080905-11509.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080906-12199.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-67988.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-54292.png)
解析
试题分析:(I)先令n=1,得
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-32157.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-13301.png)
然后再令
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-18609.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-78863.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-29087.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-22736.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-91375.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080905-58642.png)
(II)在(I)的基础上,可求出
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080909-50551.png)
(Ⅰ)当
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080909-25472.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-32157.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080909-65587.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-13301.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-18609.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-78863.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-29087.png)
两式相减得:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-22736.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080908-91375.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080909-96744.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080910-92213.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080910-72780.png)
∴数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080910-52366.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080910-43194.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080910-64100.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080911-36575.png)
(Ⅱ)由(Ⅰ)知
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080909-50551.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080911-82757.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080912-78777.png)
由①-②得:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080912-33058.png)
…………………9分
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080912-81614.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080912-96643.png)
点评:(I)再由Sn求an时,应先确定a1,然后再根据
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080912-81700.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080907-18609.png)
(II)当一个数列的通项是一个等差数列与一个等比数列积时,可以采用错位相减法求和.
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080823-74767.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080823-22277.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080834-91598.png)
且满足:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080834-49908.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080834-39840.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080835-10188.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080835-19998.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080813-10811.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080814-23902.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080814-39368.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080814-99453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080814-64793.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080815-27929.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080804-58181.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080805-95598.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080804-58181.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080805-22376.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080749-36332.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-48309.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-93653.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-12840.png)
(Ⅰ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080749-36332.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-48309.png)
(Ⅱ)记
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-20232.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-45745.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080751-73607.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080750-45745.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080743-73521.png)
A.22 | B.18 | C.20 | D.13 |
最新试题
- 1计算:(1)(﹣125)÷(﹣5);(2)(﹣1)10×2+(﹣2)3÷4.
- 2下列说法错误的是( )。A.含氧化合物不一定是氧化物B.纯净物都是由一种物质组成的C.由一种元素组成的纯净物不一定是单
- 3下面叙述中不符合骨骼肌的特性的是[ ]A.两端的肌腱分别固着在同一骨的两端B.两端的肌腱分别固着在不同的骨上C.
- 4Do you have two ________. [ ]A. pencil case B. penci
- 5Some people said _____ that Copenhagen Conference 2009 didn"
- 6下面的对联都是赞颂古代名人的。请写出其中一副对联所赞颂的人物、与对联内容相关的成语或诗句。(1)两表酬三顾,一对足千秋。
- 7I can’t spend _________ money on the car which is _________
- 8-7+______=21.
- 9与终边相同的角,则
- 101895——1898年,康有为多次上书光绪皇帝,主张( )A.师夷长技,自强求富B.救亡图存,变法自强C.驱除鞑虏,恢
热门考点
- 1某生产队春播2000公顷小麦,每天比预计多播50公顷,因此提前2天完成,求实际播种天数.
- 2地球绕太阳的运动轨道可近似为圆形,若它的运行周期T的平方与其轨道半径r的立方之比为k,不计其他天体对地球的作用力,则下列
- 3下列词语中字形完全正确的一项是( )(2分)A.阻遏肃穆地窑眼花瞭乱B.狼籍尴尬塌败张惶失措C.交卸锁屑烦燥大庭广众
- 4一杯溶液里各部分的性质是[ ]A.不相同的 B.相同的 C.上面跟下面不同 D.无法比较
- 5小惠测量一根木棒的长度,由四舍五入得到的近似数为2.8米,则这根木棒的实际长度的范围是( )A.大于2米,小于3米B.
- 6下列体现德意志帝国宪法的专制主义色彩的有 ①皇帝有权任命帝国首
- 7已知函数,过两点的直线的斜率记为.(1)求的值;(2)写出函数的解析式,求在上的取值范围.
- 8His sudden ______ of violent anger put an unpleasant end to
- 9北京位于________平原的北部边缘,背靠群山。地势特点是_______________________,从西北出居庸
- 10Dr. Ma used to two or three persons in the hospit