SOLUTION: the 3rd term of a Gp is 10 and the 6th term is 80. find 1. the Gp 2. the nth term of the Gp hence 3. the 9th term

Question 1086447: the 3rd term of a Gp is 10 and the 6th term is 80.
find
1. the Gp
2. the nth term of the Gp hence
3. the 9th term

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
the 3rd term of a Gp is 10 and the 6th term is 80.
find
1. the Gp
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ar^2 = 10
ar^5 = 80
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Divide bottom equation by top to get:
r^3 = 8
r = 2
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Then solve for "a"::
a*2^2 = 10
a = 10/4 = 5/2
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Gp:: (5/2)*2^(n-1) for n = 1,2,3...
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2. the nth term of the Gp hence::a(n) = (5/2)*2^(n-1)
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3. the 9th term :: (5/2)2^8 = 640
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Cheers,
Stan H.
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