Question

arithmetic formula ​

Answer 1

S = (n/ 2) x (a1 + an)

Where:

S = the sum

n = the number of terms in the series

a1 = the first term in the series

an = the last term in the series

Answer 2

here is the answer

An arithmetic sequence can also be defined recursively by the formulas a1 = c, an+1 = an + d, in which d is again the common difference between consecutive terms, and c is a constant. The sum of an infinite arithmetic sequence is either ∞, if d > 0, or - ∞, if d < 0.

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