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Math Help - Is it necessary to prove this or is it redundant

  1. #1
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    Is it necessary to prove this or is it redundant

    Hi,

    this post is connected to How to prove it post. Since then i have been reading about how to use proofs but am still a newbie in the area. so my question to you guys is: Is this relevant to be proven or am i just wasting my time?

    What I have is an array A of numbers. Every number in this array has an index. the indexes span from 0 to n. initial boundary conditions that are given are:

    1. i \in n is index and 0 \leq i \leq n
    2. A[i] is a value, a number in array A at position i and 0 \leq A[i] \leq n - i


    Is is necessary to prove:

    Prove that for every 0 \leq i \leq n - A[i] there exists j \in n such that j - A[i] = i.

    or is this totally redundant and obvious form the initial conditions since all i need to do is to plug-in the expression for j and show that it equals to i (of course if this is the correct way to prove this ).

    thank you

    Baxy


    PS

    Also what confuses me is this 0 \leq i \leq n - A[i] condition. Do i need some how show that if this condition isn't met then j > n can appear ??
    Last edited by baxy77bax; August 17th 2012 at 04:12 AM.
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  2. #2
    MHF Contributor
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    Re: Is it necessary to prove this or is it redundant

    What do you mean by j \in n?
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  3. #3
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    Re: Is it necessary to prove this or is it redundant

    well yes this is wrong it should be

    0\leq j \leq n

    but this i somehow passed , or at least i think i did. i posted the solution that does not include the above example since i decided it was redundant i the Please help: proof involvim array elements :CS post. thanx
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