2009 AMC 12B Problems/Problem 12
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Problem
The fifth and eighth terms of a geometric sequence of real numbers are and
respectively. What is the first term?
Solution
Let the th term of the series be
. Because
it follows that
and the first term is
. The answer is
.
See also
2009 AMC 12B (Problems • Answer Key • Resources) | |
Preceded by Problem 11 |
Followed by Problem 13 |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | |
All AMC 12 Problems and Solutions |
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