Answer :

MisterBigBrain

Answer:

S₈₀ = 5840

Explanation:

Find the first and the last term.

a₁   =  2 x 1 - 8

a₈₀ =  2 x 80 - 8

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Calculate.

a₁    =  -6

a₈₀  =  152

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Use the formula for the sum of a finite arithmetic series.

                    a₁ + a₈₀

s₈₀ = 80  x   ----------

                        2

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Use substitution.

                      -6 + 152

 s₈₀ = 80   x   ------------

                            2

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Calculate.

s₈₀   = 5840

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