2009 AMC 12A Problems/Problem 7
Problem
The first three terms of an arithmetic sequence are , , and respectively. The th term of the sequence is . What is ?
Solution
As this is an arithmetic sequence, the difference must be constant: . This solves to . The first three terms then are , , and . In general, the th term is . Solving , we get .
See Also
2009 AMC 12A (Problems • Answer Key • Resources) | |
Preceded by Problem 6 |
Followed by Problem 8 |
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All AMC 12 Problems and Solutions |
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