新题展(数列)
New University Entrance Examination（2014）
Abstract
先做两道题,如遇麻烦,尽可能再理一理思路,如果还不能解决问题,看一看提示,做好后,对一对答案,最后结合命题者的反思,自己也反思一下.
做一做
1.已知数列{an},Sn是数列{an}的前n项和.
(1)已知数列{an}是公差不为0的等差数列.
①若a2·a9=130,a4+a7=31,求数列{an}的通项公式;
②记bn=Sn/n,n∈N*,且b1,b2,b4成等比数列,证明:Snk=n2Sk(k,n∈N*).
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