SOLUTION: The sum of first three terms of a finite geometric series is -(7/10) and their product is -(1/125). [Hint: Use a/r, a, and ar to represent the first three terms, respectively.] The
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Question 1042363: The sum of first three terms of a finite geometric series is -(7/10) and their product is -(1/125). [Hint: Use a/r, a, and ar to represent the first three terms, respectively.] The three numbers are _____, _____, and _____.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The sum of first three terms of a finite geometric series is -(7/10) and their product is -(1/125). [Hint: Use a/r, a, and ar to represent the first three terms, respectively.] The three numbers are _____, _____, and _____.
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a/r + a + ar = -7/10
(a/r)*a*(ar) = -1/125
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a^3 = -1/125
a = -1/5
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Solve for "r"::
a/r = (-1/5)/r = -1/(5r)
a = -1/5
a*r = (-1/5)r
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So, -1/(5r) + (-1/5) + -r/5 = -7/10
Multiply thru by 10r to get:
-2 - 2r -2r^2 = -7r
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2r^2 -5r + 2 = 0
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r = 2
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1st term:: a/r = (-1/5)/(2) = -1/10
2nd term:: a = -1/5 = -2/10
3rd term:: a*r = (-2/10)(2) =-4/10
Note: Sum = -7/10
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Cheers,
Stan H.
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