1.若等比数列{an}满足anan+1=16n,则公比q为( )
A.2 B.4 C.8 D.16
答案:B
解析:由anan+1=16n,可得an+1an+2=16n+1,
两式相除得,=16,∴q2=16.
∵anan+1=16n,可知公比q为正数,∴q=4.
2.在正项等比数列{an}中,a2,a48是方程2x2-7x+6=0的两个根,则a1·a2·a25·a48·a49的值为( )
A. B.9 C.±9 D.35
答案:B
解析:依题意知a2·a48=3.又a1·a49=a2·a48==3,a25>0,
∴a1·a2·a25·a48·a49==9.选B.
