已知等差数列{an}满足2a2-+2a12=0,且{bn}是等比数列,若b7=a7,则b5b9=( )
A.2 | B.4 | C.8 | D.16 |
已知正项数列{an}满足a1=1,(n+2)an+12-(n+1)+anan+1=0,则它的通项公式为( ).
A.an=![]() |
B.an=![]() |
C.an=![]() |
D.an=n |
已知{an}为等差数列,其公差为-2,且a7是a3与a9的等比中项,Sn为{an}的前n项和,n∈N*,则S10的值为( )
A.-110 | B.-90 | C.90 | D.110 |
公比为2的等比数列{an}的各项都是正数,且a3a11=16,则log2a10=( )
A.4 | B.5 | C.6 | D.7 |
在等差数列{an}中,首项a1=0,公差d≠0,若am=a1+a2+…+a9,则m的值为( )
A.37 | B. 36 | C.20 | D.19 |