Réponse :
16x² - 40x + 16 = (2x -4)(8x -4)
car (2x -4)(8x -4) = 16x² -8x -32x + 16 = 16x² - 40x + 16
16x² - 49 = (4x -7)(4x +7)
56x + 49 + 16x² = (4x)² + 2(4*7*x) + 7² = (4x +7)²
49x² - 56x + 16 = (7x)² - 2(7*4*x) + 4² = (7x - 4)² = (4 - 7x)²
49x² - 16 = (7x)² - 4² = (7x - 4)(7x +4)
j'espère avoir aidé
