设Sn是等差数列{an}的前n项和,若a5a3=59,则S9S5=()A.1B.-1C.2D.12-数学

题目简介

设Sn是等差数列{an}的前n项和,若a5a3=59,则S9S5=()A.1B.-1C.2D.12-数学

题目详情

设Sn是等差数列{an}的前n项和,若
a5
a3
=
5
9
,则
S9
S5
=(  )
A.1B.-1C.2D.
1
2
题型:单选题难度:偏易来源:福建

答案

设等差数列{an}的首项为a1,由等差数列的性质可得
a1+a9=2a5,a1+a5=2a3,
s9
s5
=
a1+a9
2
×9
a1+a5
2
×5
=
9a5
5a3
=class="stub"9
5
×class="stub"5
9
=1,
故选A.

更多内容推荐