Question

数学问题: 等差数列{an},{bn}的前n项和分别为Sn,Tn,若Sn/Tn＝2n/3n+1,则an/bn等于多少?

Answer 1

an/bn

=2an/2bn

=[a1+a(2n-1)]/[b1+b(2n-1)]

={[a1+a(2n-1)]*(2n-1)/2}/{[b1+b(2n-1)]*(2n-1)/2}

=S(2n-1)/T(2n-1)

=2(2n-1)/[3(2n-1)+1]

=(4n-2)/(6n-2)

=(2n-1)/(3n-1)