问题 填空题
等差数列{an},{bn}的前n项各分别为Sn,Tn
Sn
Tn
=
3n-1
2n+3
,则
a9
b9
=______.
答案

等差数列中S2n-1=(2n-1)•an,∵

Sn
Tn
=
3n-1
2n+3

a9
b9
=
S17
17
T17
17
=
S17
T17
=
3×17-1
2×17+3
=
50
37

故答案为:

50
37

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