hey, just need a hint if you don't mind mates!
The first 3 terms of a geometric progression are also the 1st, 9th , 11th terms of an arithmetic progression.
Given that the terms of the geometric progression are all different, find the common ratio, r.
I've started with: a + ar + ar2 = a + (a+8r) + (a+10r)
ar + ar2 - 18r= 2a
i also thought about doing a system of equations but don't really know where i'm going really
Thanks for your help