A sequence is geometric sequence if the sequence reveals a common ratio. To get the common ratio divide the 2nd term with the first term or the 3rd term with the 2nd term, ....:
Examples of sequences
1. 1, 5, 25, 125....
5 = 5 the common the ratio is 5 indicated as r= 5 the ratios were all checked
1 ( don't jump to conclusion if only one ratio is tested..)
25 = 5
5
125 =5
25
2. 100, 50, 25, 5......
50 = 1 r= 1
100 2 2
25 = 1
50 2
5 = 1
25 2
In # 3 the common ratio of the geometric sequence , r= 1/2
Practice Test
Find the common ratio of the following geometric sequences
1. 1, 4, 16, 64 ...
2. 1/2, 1, 2, 4,....
3. 500, 250, 125, ....
4 1/9, 1, 9, 81,...
5. -5, 25, - 125,....
6. 1/3, 1/9, 1/27, . . .
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