Bonjour
=> 16x²+72x + 81 = (4x+9)²
=> x²+ 6x+9 = (x²+3)²
=> 4x² - 20x+25 = (2x-5)²
=> 9x² - 42x+49 = (3x-7)²
=> 49x² - 9 = (7x-3)(7x+3)
=> 121x² - 64 = (11x-8)(11x+8)
Exemple 3
A = (x+7) (x+7)
B = (2x+3)(2x-3)
C = (3x-5)(3x+5)
D = (6x-1)(6x+1)
E = (2x-5+4)(2x-5-4)=(2x-1)(2x-9)
F=(x+2+3x+1)(x+2-3x-1)=(4x+3)(-2x+1)
Bon courage.