series question | Mathematics | Page 1

vivid forge Oct 7, 2023, 4:22 AM

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I got the first part and third part right but I can't get the second part with the formula HELPPPP

livid solar Oct 7, 2023, 5:44 AM

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can you use geometric series formula? i think its geometric...?

vivid forge Oct 7, 2023, 5:45 AM

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si it was geometric i got the answer from a friend but i dont have the steps i want to understand

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i think the n+1 is throwing my answer off

livid solar Oct 7, 2023, 5:48 AM

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hold on whats the geometric series formula again 😭
$\frac{a(r^{n}-1)}{r-1}$

main starBOT Oct 7, 2023, 5:48 AM

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!𒐪 ɹɐupoɯ⇂ㄥ8𝟝 𒐪!

livid solar Oct 7, 2023, 5:48 AM

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yea ok

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a here is 4/9 is it not

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also i guess you can simplfy your denominator

solid axle Oct 7, 2023, 8:01 AM

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No, a = 2, r = 2/9. Because this holds for sum(n = 0, inf) ar^n.

solid axle Oct 7, 2023, 8:02 AM

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Let's reverse-engineer the formula. We start with: sum(i = 0, n) ar^i = a + ar + ar^2 + ar^3 + ... + ar^nright?

hollow beacon Oct 7, 2023, 4:02 PM

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The geometric series formula is (1-r^(n+1))/(1-r)

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Here |r|<1 so the sum of the series has the form 1/(1-r)

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So 2*(1/(1-r) here

livid solar Oct 7, 2023, 5:05 PM

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oh starts at 0
oops
thanks

#series question