How do you tell whether the sequence #5, 10, 20, 40, 80, ...# is geometric?

1 Answer
Mar 15, 2017

Answer:

You can tell if #f(n+1)/f(n)=#some number that is the same for all the numbers in the series

Explanation:

#10/5=2#

#20/10=2#

#40/20=2#

#80/40=2#

All these terms have a common ratio of 2. That means, if you take the next term up and divide it with the first term, you will always get this common ratio if it's a geometric series.
Since when you divide them, you always get the common ratio, that means the series is geometric.