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Math Help - Series G.P

  1. #1
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    Series G.P

    The nth term of a G.P is 51-n find a and r.
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  2. #2
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    Re: Series G.P

    note that 5^{1-n} = \frac{5}{5^n}

    so ...

    ar^n = \frac{5}{5^n}

    can you dtermine a and r now?
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  3. #3
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    Re: Series G.P

    thank you
    but Un = arn-1 not arn and the answer is a =1 and r = 1/5
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  4. #4
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    Re: Series G.P

    Quote Originally Posted by wantanswers View Post
    thank you
    but Un = arn-1 not arn and the answer is a =1 and r = 1/5
    depends on where you start n ... 0 or 1.
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