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Math Help - summation help

  1. #1
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    Angry summation help

    which of the following express 1+2+4+8+16+32 in sigma notation?
    a.) 2^(k-1) from k=1 to 6
    b.) 2^k from k=0 to 5
    c.) 2^(k+1) from k= -1 to 4

    I don't understand, isn't it all of them??

    Also, use formulas to evaluate:
    (1-k)*(2-k) from k=0 to k=n

    I'm confused on this problem because I only know formulas for summations from k=1 to k=n. Anyone know how to do this one?
    Thanks!!
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  2. #2
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    yes, choices a, b, and c are all the same and are each expressions of the series
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by mathh18 View Post
    which of the following express 1+2+4+8+16+32 in sigma notation?
    a.) 2^(k-1) from k=1 to 6
    b.) 2^k from k=0 to 5
    c.) 2^(k+1) from k= -1 to 4

    I don't understand, isn't it all of them??
    yes it is. but perhaps you are to conform to a certain definition. for instance, they may expect you to start from k = 0, or k = 1. starting at k = -1 seems awkward at this level

    Also, use formulas to evaluate:
    (1-k)*(2-k) from k=0 to k=n

    I'm confused on this problem because I only know formulas for summations from k=1 to k=n. Anyone know how to do this one?
    Thanks!!
    Hint: (1) \sum_{k = 0}^nf(k) = f(0) + \sum_{k = 1}^nf(k)

    (2) you have \sum_{k = 0}^n (2 - 3k + k^2)
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  4. #4
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    thank you!
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