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    How would I go about a question if it's 'n' in the series and not 'r'? I'm doing question 10 (ii) but I don't understand the mark scheme.

    http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf
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    (Original post by amelienine)
    How would I go about a question if it's 'n' in the series and not 'r'? I'm doing question 10 (ii) but I don't understand the mark scheme.

    http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf
    \sum\limits_{r=0}^n 2n means for each value of r, the corresponding term is 2n, which is independent of r. There are n+1 values of r.

    Hence \sum\limits_{r=0}^n 2n = 2n(n+1).
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    (Original post by SherlockHolmes)
    \sum\limits_{r=0}^n 2n means for each value of r, the corresponding term is 2n, which is independent of r. There are n+1 values of r.

    Hence \sum\limits_{r=0}^n 2n = 2n(n+1).
    Why are there n+1 vales of r?
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    (Original post by amelienine)
    Why are there n+1 vales of r?
    r = 0,1,...,n.

    I think of this as n values from 1 to n and then you add 1 for 0.
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    (Original post by SherlockHolmes)
    r = 0,1,...,n.

    I think of this as n values from 1 to n and then you add 1 for 0.
    Oh okay, thank you!
 
 
 
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