Question 135178: Find the sum of a geometric series for which a1 = 48, an = 3, and r = -1/2: *
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Find the sum of a geometric series for which a(1) = 48, an = 3, and r = -1/2
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If a(n) = 3
3 = 48(-1/2)^(n-1)
3/48 = (-1/2)^(n-1)
1/16 = (-1/2)^(n-1)
n-1 = 4
n = 5
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S(5) = 48[(-1/2)^5-1]/[(-1/2)-1]
S(5) = 48[(-33/32)]/[(-3/2)]
S(5) = 48[11/16]
S(5) = 33
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48+(-24)+12+(-6)+3 = 63-30 = 33
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Cheers,
Stan H.
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