Pour factoriser ces expressions, nous allons d'abord factoriser par groupe commun :
a. (+1)(4+9)−5(+1)(x+1)(4x+9)−5(x+1) = (+1)[(4+9)−5](x+1)[(4x+9)−5] = (+1)(4+9−5)(x+1)(4x+9−5) = (+1)(4+4)(x+1)(4x+4)
b. (+1)(8−3)+4+4(x+1)(8x−3)+4x+4 = (+1)(8−3)+(4)(+1)(x+1)(8x−3)+(4)(x+1) = (+1)(8−3+4)(x+1)(8x−3+4) = (+1)(8+1)(x+1)(8x+1)
c. (+1)(9−5)−7−7(x+1)(9x−5)−7x−7 = (+1)(9−5)−(7)(+1)(x+1)(9x−5)−(7)(x+1) = (+1)(9−5−7)(x+1)(9x−5−7) = (+1)(9−12)(x+1)(9x−12)
