Développer :
B = (3x + 4)² - 81
B = 9x² + 24x + 16 - 81
B = 9x² + 24x - 65
Factoriser :
B = (3x + 4)² - 81
B = (3x + 4)² - 9²
B = [(3x + 4) - 9] [(3x + 4) + 9]
B = (3x - 5) (3x + 13)
Calculer B pour x = - 5
B = 9x² + 24x - 65
B = 6 * - 5² + 24 * - 5 - 65
B = 6 * 25 - 120 - 65
B = 150 - 185
B = - 25
Calculer B pou x = 5/3
B = 9x² + 24x - 65
B = 9 * 5/3² + 24 * 5/3 - 65
B = 9 * 5²/3² + 120/3 - 65
B = 9 * 25/9 + 120/3 - 65
B = 225/9 + 120/3 - 65
B = 75 x 3 / 3 x 3 + 120/3 - 65 x 3 / 1 x 3
B = 75/3 + 120/3 - 195/3
B = 195/3 - 195/3
B = 0