已知等差数列an,bn的前n项和为Sn和Tn且Sn/Tn=(4n-5)/(7n+1),则a8/b8=

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已知等差数列an,bn的前n项和为Sn和Tn且Sn/Tn=(4n-5)/(7n+1),则a8/b8=

已知等差数列an,bn的前n项和为Sn和Tn且Sn/Tn=(4n-5)/(7n+1),则a8/b8=
已知等差数列an,bn的前n项和为Sn和Tn且Sn/Tn=(4n-5)/(7n+1),则a8/b8=

已知等差数列an,bn的前n项和为Sn和Tn且Sn/Tn=(4n-5)/(7n+1),则a8/b8=
a8/b8=2a8/2b8=(a1+a15)/(b1+b15)=15(a1+a15)/15(b1+b15)
=[15(a1+a15)/2]÷[15(b1+b15)/2]=S15/T15=(4*15-5)/(7*15+1)=55/106

Sn/Tn=(4n-5)/(7n+1)
2a8=a1+a15,2b8=b1+b15
a8/b8=2a8/2b8
=(a1+a15)/(b1+b15)
=[15(a1+a15)]/[15(b1+b15)]
=[15(a1+a15)/2]/[15(b1+b15)/2]
=S15/T15
=(4*15-5)/(7*15+1)
=55/106

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