已知等差数列{an},{bn}前n项和分别为Sn,Tn,已知SnTn=n+12,则a11b11=______.-数学

题目简介

已知等差数列{an},{bn}前n项和分别为Sn,Tn,已知SnTn=n+12,则a11b11=______.-数学

题目详情

已知等差数列{an},{bn}前n项和分别为Sn,Tn,已知
Sn
Tn
=
n+1
2
,则
a11
b11
=______.
题型:填空题难度:中档来源:不详

答案

∵在等差数列中S2n-1=(2n-1)•an,
a11=
S21
21
b11=
T21
21

a11
b11
=
S21
T21

又∵
Sn
Tn
=class="stub"n+1
2

S21
T21
=11
a11
b11
=11
故答案为:11

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