Niveau 3° Factoriser en utilisant toutes es identités remarquable du facteur commun A=x²+2x+1+(5x-1)(x+1) B=(x+5)(3x+4)+9x²-16 c=25x²-70x+49+6x(5x-7)

A = x² + 2x + 1 + (5x-1)(x+1)
A = (x + 1)² + (5x - 1)(x + 1) 
A = (x + 1)[(x + 1) + (5x - 1)]
A = (x + 1)(x + 5x + 1 - 1)
A = 6x*(x + 1)

B = (x+5)(3x+4) + 9x² - 16
B = (x + 5)(3x + 4) + (3x - 4)(3x + 4)  ## tu utilises l'identité remarque a² - b² = (a +b)(a - b)
B = (3x + 4)[(x + 5) + (3x - 4)]
B = (3x + 4)(4x + 1)

C = 25x² - 70x + 49 + 6x(5x-7)
C = (5x - 7)² + 6x(5x - 7)
C = (5x - 7)[(5x - 7) + 6x)
C = (5x - 7)(11x - 7)