(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

If a.a=a for all elements of R, prove R is commutative.

3. The attempt at a solution

(a+b)^{2}=a+b=a^{2}+ba+ab+b^{2}=a+ba+ab+b

Then -ba=ab

Any suggestions of how to show that -b=b?

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# Homework Help: If a.a=a prove R is commutative

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