2013经济类联考数学模拟练习二（11-15）
11.等比数列{http://file.koolearn.com/2014/0118/20140118010325910.gif
}中的
http://file.koolearn.com/2014/0118/20140118010325765.gif
，那么
http://file.koolearn.com/2014/0118/20140118010325997.gif
等于( )
(A)5 (B)-5 (C)-8 (D)8 (E)0
12.已知等差数列{
http://file.koolearn.com/2014/0118/20140118010325910.gif
}中的
http://file.koolearn.com/2014/0118/20140118010326875.gif
与
http://file.koolearn.com/2014/0118/20140118010326113.gif
是方程
http://file.koolearn.com/2014/0118/20140118010327395.gif
的两个根，那么
http://file.koolearn.com/2014/0118/20140118010327887.gif
等于
(A)3 (B)4 (C)-3 (D)-4 (E)5
13.数列{
http://file.koolearn.com/2014/0118/20140118010325910.gif
}前
http://file.koolearn.com/2014/0118/20140118010328642.gif
项和
http://file.koolearn.com/2014/0118/20140118010328841.gif
满足
http://file.koolearn.com/2014/0118/20140118010329435.gif
，则{
http://file.koolearn.com/2014/0118/20140118010325910.gif
}是( )
(A)等差数列 (B)等比数列
(C)既是等差数列又是等比数列 (D)既非等差数列亦非等比数列
(E)以上答案均不正确
14.已知数列{
http://file.koolearn.com/2014/0118/20140118010325910.gif
}的前
http://file.koolearn.com/2014/0118/20140118010328642.gif
项和
http://file.koolearn.com/2014/0118/20140118010328841.gif
是
http://file.koolearn.com/2014/0118/20140118010328642.gif
的二次函数，且它的前三项
http://file.koolearn.com/2014/0118/20140118010329130.gif
则
http://file.koolearn.com/2014/0118/20140118010330359.gif
等于( )
(A)393 (B)394 (C)395 (D)396 (E)397
15.在等差数列{
http://file.koolearn.com/2014/0118/20140118010325910.gif
}中 ,
http://file.koolearn.com/2014/0118/20140118010330659.gif
,则满足
http://file.koolearn.com/2014/0118/20140118010330859.gif
的所有
http://file.koolearn.com/2014/0118/20140118010328642.gif
的值为( )
(A)4或9 (B)4 (C)9 (D)3或8 (E)3或9
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