Sagot :
bonsoir
A = 3 x² - 12 x + 2 x² - 8 x + x - 4
= 5 x² - 19 x - 12
A = ( x - 4 ) ( 3 x + 2 x + 1 )
= ( x - 4 ) ( 5 x + 1 )
tu remplaces x par 0 et 4
1 ) A = 3x(x - 4) + (2x + 1)(x - 4)
= 3x² - 12x + 2x²+ x - 8x - 4
= 5x² - 19x - 4
2) A = 3x(x - 4) + (2x + 1)(x - 4)
= (x - 4)(3x + 2x + 1)
= (x - 4)(5x + 1)
3) (Ici on va utiliser l'expression factorisée de A)
(Pour x=0)
A = (x - 4)(5x + 1)
= (0 - 4)(5 × 0 + 1)
= -4 × 1
= -4
(Pour x=4)
A = (x - 4)(5x + 1)
= (4 - 4)(5 × 4 + 1)
= 0 × 21
= 0