SOLUTION: Find the sum of the arithmetic sequence. 6+3.5+1-1.5-4-...-49

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Question 741042: Find the sum of the arithmetic sequence.
6+3.5+1-1.5-4-...-49
Answer by reviewermath(1029) About Me  (Show Source):
You can put this solution on YOUR website!
The common difference is -2.5.
The first term is 6, so the nth term is -2.5n + 8.5 (please verify when n = 1).
To get the number of terms, we solve
-2.5n + 8.5 = -49
n = 23
The sum of the first n terms of an arithmetic sequence is equal to
S%5Bn%5D+=+%28n%2F2%29%28a%5B1%5D+%2B+a%5Bn%5D%29
S%5Bn%5D+=+%2823%2F2%29%286+-+49%29
S%5Bn%5D+=+highlight%28-494.5%29%29