Bonsoir,
Rappel des identités remarquables :
(a + b)² = a² + 2ab + b²
(a - b)² = a² - 2ab + b²
(a - b)(a + b) = a² - b²
2) A = (x + 2)²
A = x² + 4x + 4
B = (3 - x)²
B = 9 - 6x + x²
C = (7x + 4)²
C = 49x² + 56x + 16
D = (5x - 6)²
D = 25x² - 60x + 36
E = (2x + 3)(2x - 3)
E = 4x² - 9
Exercice 2 :
(2x - 5)² + (3x + 7)(2x - 5)
= (4x² - 20x + 25) + (6x² - 15x + 14x - 35)
= 4x² - 20x + 25 + 6x² - x - 35
= 10x² - 21x - 10
