等差数列{an},{bn}的前n项和分别为Sn,Tn,若SnTn=2n3n+1,则anbn=()A.23B.2n-13n-1C.2n+13n+1D.2n-13n+4-数学

题目简介

等差数列{an},{bn}的前n项和分别为Sn,Tn,若SnTn=2n3n+1,则anbn=()A.23B.2n-13n-1C.2n+13n+1D.2n-13n+4-数学

题目详情

等差数列{an},{bn}的前n项和分别为Sn,Tn,若
Sn
Tn
=
2n
3n+1
,则
an
bn
=(  )
A.
2
3
B.
2n-1
3n-1
C.
2n+1
3n+1
D.
2n-1
3n+4
题型:单选题难度:偏易来源:钟祥市模拟

答案

an
bn
=
2an
2bn
=
a1+a2n-1
b1+b2n-1
=
(2n-1)(a1+a2n-1
2
(2n-1)(b1+b2n-1
2
=
s2n-1
T2n-1

an
bn
=
2(2n-1)
3(2n-1)+1
=class="stub"2n-1
3n-1

故选B.

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