已知两个等差数列{an}和{bn}的前n项和分别为An,Bn,且An/Bn=(3n-3)/(2n+3),则a6/b6=

问题描述:

已知两个等差数列{an}和{bn}的前n项和分别为An,Bn,且An/Bn=(3n-3)/(2n+3),则a6/b6=

A11/B11=(33-3)/(22+3)=6/5
A11=11/2(a1+a11)=11/2(2a1+10d)=11/2(2a6)=11a6
A11=a1*11+11(11-1)d/2=11/2(2a1+10d)=11a6
同理b11=11b6
a6/b6=A11/B11=6/5