Question

Prove that x is odd, if and only if, x^2 is congruent to 1 (mod 4)

Answer 1

do you have a picture?

Answer 2

It's a mathematical proof, so x^2 = 1 (mod 4) the equals should be three lines.

Answer 3

How far did you get?

Answer 4

This may be a bit of overkill, but here is how a proof might go.