SOLUTION: The sum of the first nine terms of an arithmetic function is 81. if the sum of the first and third terms is zero, find the first term and the common difference. It's an arithme

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Question 1146193: The sum of the first nine terms of an arithmetic function is 81. if the sum of the first and third terms is zero, find the first term and the common difference.
It's an arithmetic sequence/ progress. Help?
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


If the sum of the first and third terms is 0, then the second term is 0; and the first and third terms are -d and d, where d is the common difference.

Then the sum of all 9 terms is the sum of the 4th through 9th terms; those terms are 2d, 3d, ..., and 7d. So

2d%2B3d%2B4d%2B5d%2B6d%2B7d+=+81

Solve that to find d to complete the problem.