Εισαγωγή στους αρνητικούς αριθμούς Original Khan Academy video: Negative Numbers Introduction https://www.khanacademy.org/math/pre-algebra/negatives-absolute-value-pre-alg/add-sub-negatives-pre-alg/v/negative-numbers-introduction Help us caption & translate this video! http://amara.org/v/CL7z/