∀ {R : Type r} [inst : CommRing R] {W' : WeierstrassCurve.Projective R} [NoZeroDivisors R] {P Q : Fin 3 → R},
  Q 2 ≠ 0 → P 0 * Q 2 = Q 0 * P 2 → P 1 * Q 2 = Q 1 * P 2 → P 1 * Q 2 = W'.negY Q * P 2 → P 1 = W'.negY P