Show that if 3 divides n^2, 3 divides n. Hint: n can only be in the form 3a, 3a + 1, 3a + 2(adsbygoogle = window.adsbygoogle || []).push({});

Can someone help me with this? It's pretty simple, I just don't know how to express it mathematically.

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# Show that if 3 divides n^2, 3 divides n

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