【简答题】A.The police want to talk to the main actor. B.The main actor forgot to come. C.The main actor is delayed by traffic. D.The actor is busy buying jam on his way.
【简答题】已知公比为q(0<q<1)的无穷等比数列{a n }各项的和为9,无穷等比数列{a n 2 }各项的和为 81 5 . (1)求数列{a n }的首项a 1 和公比q; (2)对给定的k(k=1,2,3,…,n),设T (k) 是首项为a k ,公差为2a k -1的等差数列,求T (2) 的前2007项之和; (3)(理)设b i 为数列T (i) 的第i项,S n =b 1 +b 2 +…+b...
【简答题】已知等比数列{a n }的首项为a 1 =2,公比为q(q为),且满足3a 3 是8a 1 与a 5 的等差中项;数列{b n }满足2n 2 -(t+b n )n+ 3 2 b n =0(t∈R,n∈N * ). (1)求数列{a n }的通项公式; (2)试确定t的值,使得数列{b n }为等差数列; (3)当{b n }为等差数列时,对任意k,在a k 与a k+1 之间插入2共...