等差数列{an},{bn}的前n项和Sn,Tn满足Sn/Tn=3n+1/2n+5则a5/b5=___,a3/b3=___

an = a1+(n-1)d1
bn = b1+(n-1)d2
Sn/Tn = (2a1+(n-1)d1)/(2b1+(n-1)d2) = (3n+1)/(2n+5)
put n=9
a5/b5 =(a1+4a1)/(b1+4d2) = 28/23
put n= 5
a3/b3 = (a1+2d1)/(b1+2d2)= 16/15

S9=a1+a2+.....a9=(a1+a9)+(a2+a8)+....+a5=9a5
T9=9b5
a5/b5=S9/T9
带入Sn/Tn=3n+1/2n+5
n=9时：a5/b5=28/23
同理a3/b3=S5/T5=16/15
请采纳谢谢！！！

S9/T9=(27+1)/(18+5)[(a1+a9)*9/2]/[(b1+b9)*9/2]=28/23(a1+a9)/(b1+b9)=28/232a5/2b5=28/23a5/b5=28/23S5/T5=16/15[(a1+a5)*5/2]/[(b1+b5)*5/2]=16/15(a1+a5)/(b1+b5)=16/15∴2a3/2b3=16/15∴a3/a5=16/15明教为您解...

S9/T9=(27+1)/(18+5)
[(a1+a9)*9/2]/[(b1+b9)*9/2]=28/23
(a1+a9)/(b1+b9)=28/23
2a5/2b5=28/23
a5/b5=28/23
S5=5(a1+a5)/2=5*(2a3)/2=5a3
T5=5b3
Sn/Tn=3n+1/2n+5,
a3/b3=S5/T5=(3*5+1)/(2*5+5)=16/15,