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i have just registered to the forum, because this time i study number theory and in some problems i can't figure out how to solve them.

This time i have to prove: If two integers x,y doesn't divided with 3 then the (x^2 - y^2) always is divided with 3.

Does any one has a clue how to start?

Thank you!

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# (x^2 - y^2)

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