Quadratic character of minus three
= Quadratic character of minus three
For an odd prime $p\ne3$, quadratic reciprocity gives
$$
\left(\frac{-3}{p}\right)=\left(\frac p3\right).
$$
Thus $-3$ is a square modulo $p$ exactly when $p\equiv1\pmod3$.
= Quadratic character of minus three
For an odd prime $p\ne3$, quadratic reciprocity gives
$$
\left(\frac{-3}{p}\right)=\left(\frac p3\right).
$$
Thus $-3$ is a square modulo $p$ exactly when $p\equiv1\pmod3$.