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Proof of Quadratic Formula http://www.khanacademy.org/video/proof-of-quadratic-formula --------------------------------------- يتناول هذا الفيديو إثبات للصيغة التربيعية ---------------------------------------- شكر خاص لمؤسسة شركاء في التنمية المستدامة -- فلسطين http://psdpal.org