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Proof about addition commuting

  1. Jan 27, 2014 #1
    1. The problem statement, all variables and given/known data
    Prove by induction that 1+a=a+1 for all natural numbers
    3. The attempt at a solution
    basis step 1+1=1+1
    Now we assume that it is true for a=k and then look at k+1
    I first wanted to do this (k+1)+(k+1)=(k+1)+1 but that doesn't give me the right answer.
    so should it be (k+1)+1=(k+1)+1
    on the left side am I just adding 1 because we are looking at the next term
    and on the left side i replace 1+a with k+1 because we are assuming that holds and then looking at the next term.
    Last edited: Jan 27, 2014
  2. jcsd
  3. Jan 27, 2014 #2


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    Write down what that means so you know what you are given.

    Write down what you are trying to prove.

    That should get you started. Do you have the associative law to work with?
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