Réponse :
Bonjour
Explications étape par étape :
Exercice 1
A = 3(4x + 7) + 4x(2x - 9)
A = 12x + 21 + 8x² -36x
A = 8x² + 12x - 36x + 21
A = 8x² -24x +21
B = 7x(2x - 5) -x (2x - 5)
B = 14x² -35x - 2x² + 5x
B = 14x² -2x² -35x + 5x
B = 12x² -30x
C = (2x - 5)(3x - 2)
C = 6x² -4x -15x + 10
C = 6x² -19x + 10
D = (x + 7)(3 - 2x) + (5x - 2)(4x + 1)
D = 3x -2x² +21 -14x + 20x² +5x - 8x - 2
D = -2x² +20x² + 3x + 5x -14x - 8x + 21 - 2
D = 18x² -14x + 19
Exercice 2
a : 5 (x + 3) = 3 +(2x - 6)
a : 5x + 15 = 3 + 2x -6
a : 5x -2x = - 6 - 15 + 3
a : 3x = - 18
x = -18/3
x = -6
b : - 2(2x - 4) = 6x - (- 3x + x)
b : - 4x + 8 = 6x + 3x - x
b = - 4x - 6x - 3x + x = - 8
b : - 12x =- 8
b : x = 8/12
b : x = 2/3
Exercice 3
E = (3x + 2) (4x - 2) +(4x - 2) (x - 6)
E = (4x - 2) (3x + 2 + x - 6)
E = (4x - 2) (4x - 4)
E = 8 (x - 1) (2x - 1)
