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Sum of arithmetic series

  • Thread starter Blister
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  • #1
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Homework Statement



The sum of the first 4 terms in an arithmetic series is -8 and the sum of the first 5 terms is 85. Determine the first term and the common difference.

Homework Equations



tn = a + (n-1)d
Sn = n/2 (2a + (n-1)d)

The Attempt at a Solution

 

Answers and Replies

  • #2
rock.freak667
Homework Helper
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The Attempt at a Solution

I think you forgot to type in this section.
 

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