PARTE 1: https://es.khanacademy.org/math/algebra-home/alg-polynomials/alg-factoring-quadratics-diff-of-squares/e/factoring_difference_of_squares_2
PARTE 2: https://es.khanacademy.org/math/algebra-home/alg-polynomials/alg-finding-zeros-of-polynomials/e/find-the-zeros-of-polynomials