bjr
c'est l'application du produit remarquable (a + b)(a - b) = a² - b²
E = (-3x -1/3)(3x - 1/3) = -(3x + 1/3)(3x - 1/3) = - [(3x)² - (1/3)²] = -9x² + 1/9
F = [(1/9)x + 4/5)][(1/9)x - 4/5)] = [(1/9)x]² - (4/5)² = (1/81)x² - 16/25
G = [5/6 + (2/3)x][-5/6 + (2/3)x] =
[(2/3)x + 5/6][(2/3)x - 5/6] =
[(2/3)x]² - (5/6)² =
(4/9)x² - 25/36
H = [25/14 - (11/7)x][25/14 + (11/7)x] =
(25/14)² - [11/7)x]² = 625/196 - (121/49)x²
