等差数列{an}{bn}的前n项和分别为An,Bn,An/Bn=7n+1/4n+27,a5/b5=?_数学解答

等差数列{an}{bn}的前n项和分别为An,Bn,An/Bn=7n+1/4n+27,a5/b5=?

人气：291 ℃　时间：2020-07-07 22:49:43

解答

An/Bn=7n+1/4n+27
A9/B9=64/63
[9(a1+a9)/2]/[9(b1+b9)/2]=64/63
(9*2a5)/2)/(9*2b5/2)=64/63
a5/b5=64/63