Réponses

2013-12-09T18:07:29+01:00
B = 5(1-x +2x(x-1))
   = 5(1-x+2x(-1+x))
   = 5(1-x-2x(1-x))
   Factorisation
   = 5(1-x)[1-2x]
   = 5(1-x)(1-2x)

C = (x+4)² - (5+2x) ²
Identité : a² - b² = (a+b)(a-b)
   = (x+4 - (5+2x))(x+4 + (5+2x))
   = (x+4 - 5 - 2x) (x+4+5+2x)
   = (1-x)(3x+9)
   = (1-x)(3x + 3*3)
   = 3 (1-x)(x + 3)