问题
选择题
记数列{an}的前n项和为Sn,且Sn=2(an-1),则a2=( )
A.4
B.2
C.1
D.-2
答案
∵S1=2(a1-1),
∴a1=2
∵a1+a2=2(a2-1),
∴a2=4
故选A
记数列{an}的前n项和为Sn,且Sn=2(an-1),则a2=( )
A.4
B.2
C.1
D.-2
∵S1=2(a1-1),
∴a1=2
∵a1+a2=2(a2-1),
∴a2=4
故选A