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Math Help - I have one question about a geometric series...please help. :)

  1. #1
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    I have one question about a geometric series...please help. :)

    What are the first five partial sums of the geometric series (5/8)*3^(n-1)?

    Any help is appreciated!

    ~Caylie
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  2. #2
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    Re: I have one question about a geometric series...please help. :)

    Quote Originally Posted by Caylie View Post
    What are the first five partial sums of the geometric series (5/8)*3^(n-1)?

    Any help is appreciated!

    ~Caylie
    \displaystyle \sum_{n=1}^5 \left(\frac{5}{8} \cdot 3^{n-1}\right)=\frac{5}{8} \cdot \displaystyle \sum_{n=1}^5 3^{n-1}=\frac{5}{8} \cdot \left(3^0+3^1+3^2+3^3+3^4\right)=\frac{605}{8}
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  3. #3
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    Re: I have one question about a geometric series...please help. :)

    Quote Originally Posted by princeps View Post
    \displaystyle \sum_{n=1}^5 \left(\frac{5}{8} \cdot 3^{n-1}\right)=\frac{5}{8} \cdot \displaystyle \sum_{n=1}^5 3^{n-1}=\frac{5}{8} \cdot \left(3^0+3^1+3^2+3^3+3^4\right)=\frac{605}{8}
    This is the fifth partial sum. The first four are formed similarly.
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