问题
选择题
设等比数列{an}的前n项和为Sn,已知a1=2011,且an+2an+1+an+2=0(n∈N*),则S2012=( )
A.2011
B.2012
C.1
D.0
答案
设等比数列{an}的公比为q,∵an+2an+1+an+2=0,
∴an+2anq+anq2=0,即1+2q+q2=0,∴q=-1,
∴S2012=
=a1(1-q 2012) 1-q
=0,2011(1-1) 2
故选D.