Bonjour,

A = (3x - 2)²

Du type (a - b)² = a² - 2ab + b²

Ici a = 3x et b = 2

A = (3x)² - 2(3x × 2) + 2² = 9x² - 2 × 6x + 4

A = 9x² - 12x + 4

B = (5x - 3)² + (4 - 9x²)

B = (5x)² - 2(5x × 3) + 3² + 4 - 9x²

B = 25x² - 30x + 9 + 4 - 9x²

B = 16x² - 30x + 13

C = (7 + 4x)²

C = 7² + 2(7 × 4x) + (4x)²

C = 49 + 56x + 16x²

C = 16x² + 56x + 49

D = (5x + 3)(5x - 3)

Du type (a + b)(a - b) = a² - b²

Ici a = 5x et b = 3

C = (5x)² - 3²

C = 25x² - 9

Bonne journée !