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What is the sum of the first 20 terms of the series 3 + 14 + 25 + 25 + 36 +
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2 votes
What is the sum of the first 20 terms of the series 3 + 14 + 25 + 25 + 36 +

User Willian Vieira
by
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2 Answers

4 votes
2150 is the correct answer
User Sarah
by
5.1k points
1 vote

Answer:


S _(20) = 2150

Explanation:


a _(1) = 3 \\ a _(2) = 14 \\ d = a _(2) - a_(1) = 14 - 3 = 11 \\ n = 20


S _(n) = (n)/(2) (2a + (n - 1)d) \\ \\ S _(20) = (20)/(2) (2(3) + (20 - 1) * 11) \\ \\ S _(20) = 10 * (6 + 19 * 11) \\ S _(20) = 10 * (6 + 209) \\ S _(20) = 10 * 215 \\ S _(20) = 2150

User Cedomir Rackov
by
4.9k points
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