2010 AMC 12B Problems/Problem 20
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Problem 20
A geometric sequence has , , and for some real number . For what value of does ?
Solution
By defintion, we have . Since , we can rewrite this as .
The common ratio of the sequence is , so we can write
We can conclude that the sequence from to repeats.
Since , we have , which is making our answer , or E.
See also
2010 AMC 12B (Problems • Answer Key • Resources) | |
Preceded by Problem 19 |
Followed by Problem 21 |
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