Bonsoir,
identité remarquable :
(a - b)² = a² - 2ab + b²
(a+b)² = a² + 2ab + b²
(a + b) (a - b) = a² - b²
Donc :
D = (5x-8)²
D = (5x)² - 2 * 5x * 8 + 8²
D = 25x² - 80x + 64
E = (9x + 4)²
E = (9x)² + 2 * 9x * 4 + 4²
E = 81x² + 72x + 16
F = (7x-4) (7x + 4)
F = (7x)² - 4²
F = 49x² - 16
Bonne soirée.
