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 Description  
 Geometric Sequence:  A sequence of numbers in which the ratio between any two consecutive terms is the same. In other words, you multiply by the same number each time to get the next term in the sequence. This fixed number is called the common ratio for the sequence.
Examples of Geometric Sequences
Consider the following geometric sequences of numbers. Could you have figured out what the common ratio is in each sequence?

 Sequence
 Common Ratio
(Fixed Number Being Multiplied)
3,12,48,192..
 4
32,-16,8,-4, ...
-0.5 
 1,3,9,27,81,...
 3

As indicated in the second example, the constant factor does not have to be a positive number or even a whole number! In this case, it is -0.5.

Non-example 1, 3, 9, 19,

Although the first three terms of the above sequence gives the impression that it is a geometric sequence with common ratio 3, the fourth term 19 is not 3x9. So this sequence is not a geometric sequence.