Completamento del Quadrato

Help us caption and translate this video on Amara.org: http://www.amara.org/en/v/B2wg/ Esercizi: http://www.khanacademy.org/exercises?exid=equation_of_a_circle_2 Traduzione in Italiano del video http://www.youtube.com/watch?v=gzm-uhj06q8 http://www.khanacademy.org/video/completing-the-square?playlist=Algebra