在正项等比数列{an}中,a1,a19分别是方程x2-10x+16=0的两根,则a8·a10·a12等于( )
| A.16 | B.32 | C.64 | D.256 |
等比数列{an}中,若log2(a2a98)=4,则a40a60等于( )
| A.-16 | B.10 | C.16 | D.256 |
已知数列{an}满足3an+1+an=0,a2=-
,则{an}的前10项和等于( )
| A.-6(1-3-10) | B. |
| C.3(1-3-10) | D.3(1+3-10) |
设首项为1,公比为
的等比数列{an}的前n项和为Sn,则( )
| A.Sn=2an-1 | B.Sn=3an-2 |
| C.Sn=4-3an | D.Sn=3-2an |
等比数列{an}中,|a1|=1,a5=-8a2,a5>a2,则an等于( )
| A.(-2)n-1 | B.-(-2)n-1 |
| C.(-2)n | D.-(-2)n |
若等比数列{an}满足anan+1=16n,则公比为( )
| A.2 | B.4 | C.8 | D.16 |
公比为2的等比数列{an}的各项都是正数,且a3a11=16,则a5等于( )
| A.1 | B.2 | C.4 | D.8 |
已知数列{an}满足3an+1+an=0,a2=-
,则{an}的前10项和等于( )
| A.-6(1-3-10) | B. |
| C.3(1-3-10) | D.3(1+3-10) |
已知等比数列{an}中,a4+a8=-2,则a6(a2+2a6+a10)的值为( )
| A.4 | B.6 | C.8 | D.-9 |