Asked by Annie

the 65th term in a geometric sequence is 8000, and the 69th term is 500. find the 64th term
Answered by Reiny
ar^64 = 8000
ar^68 = 500

divide the 2nd by the 1st
r^4 = 500/8000 = 1/16
r = ± 1/2

so term 64 = term 65 / r
= 8000/(±1/2) = ± 16000