Réponse :

Factorisons les expressions :

[tex](3x-1)^2-16 = (3x-1)^2-4^{2} \\(3x-1)^2-16 = (3x-1 -4)(3x-1+4)\\(3x-1)^2-16 = (3x-5)(3x+3)[/tex]

( a² - b² = ( a - b )( a + b) )

__________________________________________

[tex]x^2+2x+1-(x+1)(2x+3) = (x+1)^2 - (x+1)(2x+3)\\x^2+2x+1-(x+1)(2x+3) = (x+1)(x+1-2x-3)\\x^2+2x+1-(x+1)(2x+3) = (x+1)(-x-2)\\x^2+2x+1-(x+1)(2x+3) = -(x+1)(x+2)[/tex]

( a² + 2ab + b² = ( a + b )²  )