2009 AMC 12A Problems/Problem 7
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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 • Resources) | ||
| Preceded by Problem 6 | Followed by Problem 8 | |
| 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 | ||
