If ppp is a prime, how many non-zero elements x∈Zpx \in \mathbb{Z}_px∈Zp satisfy x2≡a(modp)x^2 \equiv a \pmod{p}x2≡a(modp) when (ap)=−1\left( \frac{a}{p} \right) = -1(pa)=−1?
0
1
2
p-1