{an},{bn}是两个等差数列,其前n项和分别为Sn和Tn,且Sn/Tn=(7n+2)/(n+3),则a8/b8=

题目

{an},{bn}是两个等差数列,其前n项和分别为Sn和Tn,且Sn/Tn=(7n+2)/(n+3),则a8/b8=

答案

∵{an},{bn}是两个等差数列
∴a1+a15=2a8 b1+b15=2b8
∴a8/b8=(15(a1+a15)/2)/(15(b1+b15)/2)=S15/T15
∵Sn/Tn=(7n+2)/(n+3),
∴a8/b8=(7*15+2)/(15+3)=107/18.