设等差数列{an}的前n项和为Sn.若a5=5a3,则S9S5=(  ) A.10 B.9 C.12 D.5

问题描述:

设等差数列{an}的前n项和为Sn.若a5=5a3,则

S9
S5
=(  )
A. 10
B. 9
C. 12
D. 5

∵等差数列{an},a5=5a3
∴a1=-

3
2
d,
S9
S5
=9,
故选:B.