两等差数列{an}、{bn}的前n项和分别为Sn和Tn,且(2n+7)Sn=(5n+3)Tn,则a5b5的值是()A.2817B.2315C.5327D.4825-数学

题目简介

两等差数列{an}、{bn}的前n项和分别为Sn和Tn,且(2n+7)Sn=(5n+3)Tn,则a5b5的值是()A.2817B.2315C.5327D.4825-数学

题目详情

两等差数列{an}、{bn}的前n项和分别为Sn和Tn,且(2n+7)Sn=(5n+3)Tn,则
a5
b5
的值是(  )
A.
28
17
B.
23
15
C.
53
27
D.
48
25
题型:单选题难度:偏易来源:成都模拟

答案

由题意可得
Sn
Tn
=class="stub"5n+3
2n+7

a5
b5
=
9a5
9b5
=
9(a1+a9)
2
9(b1+b9)
2

=
S9
T9
=class="stub"5×9+3
2×9+7
=class="stub"48
25

故选D

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