Problem - 4206
Let $n^2$ be a square. Show that $n^2\equiv 0, 1\pmod{3}$.
If $n\equiv 0 \pmod{3}$, then $n^2\equiv 0\pmod{3}$.
If $n\equiv \pm 1\pmod{3}$, then $n^2\equiv 1\pmod{3}$.
Let $n^2$ be a square. Show that $n^2\equiv 0, 1\pmod{3}$.
If $n\equiv 0 \pmod{3}$, then $n^2\equiv 0\pmod{3}$.
If $n\equiv \pm 1\pmod{3}$, then $n^2\equiv 1\pmod{3}$.