SOLUTION: Are these sequences arithmetic, geometric, or neither? (1) 3, 5, 8, ... (2) 2a, 4a^2, 8a^3, ... I think the first is neither and the second is geometric but need guidance,

Algebra ->  Sequences-and-series -> SOLUTION: Are these sequences arithmetic, geometric, or neither? (1) 3, 5, 8, ... (2) 2a, 4a^2, 8a^3, ... I think the first is neither and the second is geometric but need guidance,      Log On


   

Question 1188227: Are these sequences arithmetic, geometric, or neither?
(1) 3, 5, 8, ...
(2) 2a, 4a^2, 8a^3, ...
I think the first is neither and the second is geometric but need guidance, thank you so much!
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

the following sequence:
(1) 3, 5, 8, ...

This sequence is not arithmetic (no common difference d), and it's not geometric ( no common ratio r) .
answer: neither

(2) 2a, 4a%5E2, 8a%5E3, ...
not arithmetic (no common difference d )

let's check common ratio:
r=4a%5E2%2F2a=2a
r=8a%5E3%2F4a%5E2=2a
The ratio between the consecutive terms is constant so we can conclude that the sequence is geometric.