Which of the following is true for x2−Dy2=−1x^2 - Dy^2 = -1x2−Dy2=−1?
It always has a solution for any DDD
It has no solution if DDD has a prime factor p≡3(mod4)p \equiv 3 \pmod{4}p≡3(mod4)
It only has solutions if DDD is a perfect square
It has solutions for D=3D=3D=3