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Bonjour

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

2)

a. 5 (x + 3) = 3 + (2x - 6)

5x + 15 = 3 + 2x - 6

5x - 2x = - 6 - 15 + 3

3x = - 18

x = - 18/3

x = - 6

b. - 2 (2x - 4) = 6x - (- 3x + x)

- 4x + 8 = 6x + 3x - x

- 4x - 6x - 3x + x = - 8

- 12x = - 8

x = 8/12

x = 2/3

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)

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)