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Arethmetic series

  1. Nov 18, 2007 #1
    Σ (-1)n
    i am meant to write it out in full and i know that the answer is 0 which i think i understand as it will be -1+1-1+1 etc, but i dont know what to do about the k, it doesn't say that it is a constant, is it safe to assume it is anyway? and what do i do if it is?
  2. jcsd
  3. Nov 18, 2007 #2


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    (-1)^n, right? Yes, k is a constant. 2k is the number of terms in -1+1-1+1... What's the sum? Hint: 2k is even.
  4. Nov 18, 2007 #3
    yes sorry, i wrote it out in word and copy pasted it, the superscript obviously didn't show up. if 2k showa that the number of terms will be even then with the pattern of -1+1 the answere will be 0...how do i write it out though? is it just -1+1 with a recurring dot? can i do that?
  5. Nov 18, 2007 #4


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    The sum is 0, yes. Just write it using words, like '(-1+1)+(-1+1)+... k times =0+0+0+... k times=0'. Something like that.
  6. Nov 18, 2007 #5
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