2015经济类联考数学数列专题2
1.数列3，12，30，60，…的一个通项公式是( )(A)
http://file.koolearn.com/2014/0219/20140219030848548.gif
(B)
http://file.koolearn.com/2014/0219/20140219030854975.gif
(C)
http://file.koolearn.com/2014/0219/20140219030857965.gif
(D)
http://file.koolearn.com/2014/0219/20140219030903991.gif
(E)以上答案均不正确
2.若数列{
http://file.koolearn.com/2014/0219/20140219030909110.gif
}的前
http://file.koolearn.com/2014/0219/20140219030914186.gif
项和
http://file.koolearn.com/2014/0219/20140219030919677.gif
，则它的通项公式是( )
(A)
http://file.koolearn.com/2014/0219/20140219030920358.gif
(B)
http://file.koolearn.com/2014/0219/20140219030920874.gif
(C)
http://file.koolearn.com/2014/0219/20140219030920129.gif
(D)
http://file.koolearn.com/2014/0219/20140219030928633.gif
(E)以上答案均不正确
3.已知{an}是等差数列，
http://file.koolearn.com/2014/0219/20140219030929720.gif
，
http://file.koolearn.com/2014/0219/20140219030934901.gif
，则
http://file.koolearn.com/2014/0219/20140219030934162.gif
等于()
(A)30 (B)27 (C)24 (D)21 (E)20
4.在等比数列{
http://file.koolearn.com/2014/0219/20140219030938201.gif
}中，已知Sn=36，S2n=54，则S3n等于
(A)63 (B)68 (C)76 (D)89 (E)86
5. 设
http://file.koolearn.com/2014/0219/20140219030942850.gif
是方程
http://file.koolearn.com/2014/0219/20140219030946872.gif
的两根，则
http://file.koolearn.com/2014/0219/20140219030946184.gif
与
http://file.koolearn.com/2014/0219/20140219030950653.gif
的等差中项A和等比中项G分别等于
(A)A=14,G=6 (B)A=14,G=
http://file.koolearn.com/2014/0219/20140219030953452.gif
6 (C)A=14,G=36 (D)A=-14,G=
http://file.koolearn.com/2014/0219/20140219030953452.gif
36
(E)以上答案均不正确
答案：1. C 2. C 3. B 4. A 5. B
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