bjr
R = (x + 4)² - 49
= (x + 4)² - 7²
on utilise a² - b² = (a - b)(a + b) ; a = (x + 4) et b = 7
a² - b² = ( a - b)( a + b)
(x + 4)² - 7² = (x + 4 - 7)(x + 4 + 7)
= (x - 3) (x + 11)
réponse
(x - 3)(x + 11)
S = (x - 4)² - (2x - 1)² ; a = x - 4 ; b = 2x - 1)
a² - b² = ( a - b ) ( a + b )
(x - 4)² - (2x - 1)² = [(x - 4) - (2x -1)][(x - 4) + 2x - 1)]
= (x - 4 -2x + 1) (x - 4 + 2x - 1)
= (-x - 3) (3x - 5)
= - (x + 3)(3x - 5)
réponse :
- (x + 3)(3x - 5)
