【简答题】已知等比数列 中, ;求(1)首项与公比;(2)
【简答题】已知集合A={x|x=-2n-1,n∈N * },B={x|x=-6n+3,n∈N * },设S n 是等差数列{a n }的前n项和,若{a n }的任一项a n ∈A∩B,首项a 1 是A∩B中的最大数,且-750<S 10 <-300. (Ⅰ)求数列{a n }的通项公式; (Ⅱ)若数列{b n }满足 b n =( 2 2 ) a n +13n-9 ,令T n =24(b 2 +b 4 +...
【简答题】已知数列{a n }是等差数列,数列{b n }是等比数列,且对任意的n∈N*,都有a 1 b 1 +a 2 b 2 +a 3 b 3 +···+a n b n =n·2 n+3 . (1)若{b n }的首项为4,公比为2,求数列{a n +b n }的前n项和S n ; (2)若a 1 =8. ①求数列{a n }与{b n }的通项公式; ②试探究:数列{b n }中是否存在某一项,它可以表...
【单选题】邻苯二甲酸酐和正丁醇在浓硫酸催化下加热合成邻苯二甲酸二正丁酯(沸点340°C),经除去硫酸、水和正丁醇,仍含有少量杂质,进一步应当用什么方法提纯?
【简答题】What does it take to be a well-trained nurse? The answer used to be two-year associate’s or four-year bachelor’s degree programs. But as the nursing shortage 1 , a growing number of schools and hospit...
【简答题】二 . Fill in the blanks in the following paragraph with the exact words that appear in your textbook . Fill in each blank with only ONE word. There are many different stories about the downturn in the ...
【简答题】阅读理解。 There are some very good things about open education. This way of teaching allows the students to grow as people, and to develop their own interests in many subjects. Open education allows stude...
【简答题】(本小题满分16分) 已知数列 是等差数列,数列 是等比数列,且对任意的 ,都有 . (1)若 的首项为4,公比为2,求数列 的前 项和 ; (2)若 . ①求数列 与 的通项公式; ②试探究:数列 中是否存在某一项,它可以表示为该数列中其它 项的和?若存在,请求出该项;若不存在,请说明理由.
【简答题】(文科做以下(1)(2)(3)) (1)、已知 ,求数列 的通项公式(6分); (2)、在(1)的条件下,数列 ,求证数列 是一个 “1类和科比数列”(4分); (3)、设等差数列 是一个 “ 类和科比数列”,其中首项 ,公差 ,探究 与 的数量关系,并写出相应的常数 (6分);