p = - x ± x 2 - 4 ( - g x 2 2 v 2 ) ( - g x 2 2 v 2 - y ) 2 ( - g x 2 2 v 2 ) p = {\frac{-x\pm\sqrt{x^2-4(\frac{-gx^2}{2v^2})(\frac{-gx^2}{2v^2}-y)}}{2(\frac{-gx^2}{2v^2}) }}