【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...
【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 ...