SOLUTION: Find the sum of the first eight terms of the arithmetic series 3 + 5 + 7 + 9 +...

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Question 709273: Find the sum of the first eight terms of the arithmetic series 3 + 5 + 7 + 9 +...
Answer by josgarithmetic(39618) About Me  (Show Source):
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The sequence of terms uses difference of 2. The beginning term is 3.

The general term of the sequence, a%5Bn%5D=3%2B%28n-1%29%2A2

The summation for n terms of an arithmetic sequence is
S=%28n%2F2%29%28a%5B1%5D%2Ba%5Bn%5D%29, using as indicated, the first and last terms in the range.

%288%2F2%29%283%2B17%29=80