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What is the sum of the first seven terms of the geometric series where a1 = 10 and r = −2?
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Apr 14, 2022
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What is the sum of the first seven terms of the geometric series where a1 = 10 and r = −2?
Mathematics
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Ralph Tandetzky
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Ralph Tandetzky
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1
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7
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Answer:
430
Explanation:
Given GP with:
a1 = 10
r = -2
To find
S7
Solution
Formula of sum:
Sn = a1(r^n - 1)/(r - 1)
Substitute values:
S7 = 10((-2)^7 - 1)/(-2 - 1) = 10(- 128 - 1)/(-3) = 10*129/3 = 430
Daveaspinall
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Apr 20, 2022
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Daveaspinall
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