设等差数列﹛an﹜﹛bn﹜的前n项和分别为Sn,Tn.且Sn/Tn=n-9/5n-9.则a8/b8=?

问题描述:

设等差数列﹛an﹜﹛bn﹜的前n项和分别为Sn,Tn.且Sn/Tn=n-9/5n-9.则a8/b8=?

a8/b8
=15a8/15b8
=(a1+a2+a3+...+a15)/(b1+b2+...+b8)
=S15/T15
=6/66
=1/11