Question

In a geometric seq. Where the first three terms are 9, -6 and 4 which term of the sequence is 256/729 ?

Answer 1

r=-6/9=-2/3

check: third term (-6)(-2/3)=4

Gr=9(-2/3)^r

256/729=9(-2/3)^r

256/9*729=-(2/3)^r so r is even..

remembering that 2^8=256
and checking that
9*720=3^2*3^6=3^8
then r=8

Answer 2

Then, since the first term is r=0, the term given must be the 9th term, at r=8