若两个等差数列{an}{bn}的前n项和分别为An、Bn,且满足An/Bn=4n+2/5n-5,则a5+a13/b5+b13的值为

若两个等差数列{an}{bn}的前n项和分别为An、Bn,且满足An/Bn=4n+2/5n-5,则a5+a13/b5+b13的值为
若两个等差数列{an}{bn}的前n项和分别为An、Bn,且满足An/Bn=4n+2/5n-5,则a5+a13/b5+b13的值为

若两个等差数列{an}{bn}的前n项和分别为An、Bn,且满足An/Bn=4n+2/5n-5,则a5+a13/b5+b13的值为
a5+a13=2a9,b5+b13=2b9
那么(a5+a13)/(b5+b13)=a9/b9=(4×9+2)/(5×9-5)
=38/40
=19/20

let
An = k1n^2 + k2n
Bn = m1n^2 + m2n

an =a1+ (n-1)d1
An = n(2a1+(n-1)d1)/2
bn =b1+ (n-1)d2
Bn = n(2b1+(n-1)d2)/2
An/Bn = (2a1+(n-1)d1)/(2b1+(n-1)d2) = (4n+2)/(5n-5)
put n=13
(2a1+12d1)/(2b1+12d2) = 44/60 = 11/15

(a5+a13)/(b5+b13)
=(2a1+12d1)/(2b1+12d2)
=11/15

a5+a13=a1+a17 b5+b13=b1+b17 所以a5+a13/b5+b17=A17/B17=7/8 结果可能错了 但计算方法一定正确