If $d$ is divisible by a prime $p \equiv 3 \pmod{4}$. show that the equation $x^2-dy^2=-1$ has no solution.
So far I have learn only positive Pell's equation but not negative Pell's equation. We know that in positive Pell's equation, it always has a solution but not the case for negative Pell's equation.
Can anyone give some hints on how to tackle this question?