Help us caption and translate this video on Amara.org: http://www.amara.org/en/v/B2wU/ Esercizi: http://www.khanacademy.org/exercise/parabola_intuition_2 Traduzione in Italiano del video Parabola Focus and Directrix 1 http://www.youtube.com/watch?v=ZJf9shWlMz0 http://www.khanacademy.org/video/parabola-focus-and-directrix-1?playlist=Algebra Help us caption & translate this video! http://amara.org/v/B2wU/