5. (2008海南、宁夏文、理)设等比数列的公比, 前n项和为,则( )
A. 2 B. 4 C. D.
4.(2005江苏)在各项都为正数的等比数列中,首项,前三项和为21,则=( )
A.84 B.72 C.33 D.189
3.(2007重庆文)在等比数列{an}中,a2=8,a5=64,,则公比q为( )
(A)2 (B)3 (C)4 (D)8
2.(2007福建文)等比数列{an}中,a4=4,则a2·a6等于( )
A.4 B.8 C.16 D.32
1.(2008福建理)设{an}是公比为正数的等比数列,若,a5=16, 则数列{an}前7项的和为( )
A.63 B.64 C.127 D.128
50. A. behind B. for C. away D. out
参考答案 (31-35) DBCAB (36-40)CCBDC (41-45)AADCD (46-50)AACAA
36
49. A. stopped B. gone C. passed D. entered
48. A. early B. late C. unexpectedly D. happily
47. A. color B. bright C. love D. dream