Warm-up exercise:Which is better "proof":Show that any square leaves remainder 0, 1 or 4 on division by 8.

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orto write all possible cases in (mod 8) class (asundefinedhelped me here)

"Obvious" from 1st exercise, but how to write a proof?Deduce that a sum of 3 squares leaves remainder 0, 1, 2, 3, 4, 5, or 6 on division by 8.

Let and be a sum of 3 squares.

Then just write all possible combinations?