Problem - 4143
Let $n^2$ be a square number, show that $n^2\equiv 0, 1\pmod{4}$.
If $n$ is odd, then $n \equiv \pm 1 \pmod{4} \implies n^2\equiv 1\pmod{4}$.
If $n$ is even, then $n\equiv 0, 2\pmod{4} \implies n^2\equiv 0\pmod{4}$
Let $n^2$ be a square number, show that $n^2\equiv 0, 1\pmod{4}$.
If $n$ is odd, then $n \equiv \pm 1 \pmod{4} \implies n^2\equiv 1\pmod{4}$.
If $n$ is even, then $n\equiv 0, 2\pmod{4} \implies n^2\equiv 0\pmod{4}$