Partie 3: des équations à développer puis à réduire = b) 2 (x - 5) – 5x = - 3x -10 d) 5 - (x - 3) = 4x - 2 (3x - 8) a) 3x - 6 (3 - 4x) = 9x - 2 c) 3x - 2x (x -

Bonjour

Développer et réduire :

b) 2 (x - 5) – 5x = - 3x -10

2x - 10 - 5x = - 3x - 10

2x - 5x + 3x = - 10 + 10

- 0x = 0

Vrai pour toutes les valeurs.

d) 5 - (x - 3) = 4x - 2 (3x - 8)

5 - x + 3 = 4x - 6x + 16

- x - 4x + 6x = 16 - 5 - 3

x = 8

a) 3x - 6 (3 - 4x) = 9x - 2

3x - 18 + 24x = 9x - 2

3x + 24x - 9x = - 2 + 18

18x = 16

x = 16/18

x = 4/9

c) 3x - 2x (x - 1) = - 2x2 +7x – 12

3x - 2x² + 2x = - 2x² + 7x - 12

- 2x² + 2x² + 3x + 2x - 7x = - 12

- 2x = - 12

x = 12/2

x = 6

e) 4 (2x – 5) – 3 (3x + 1) = - 6 (x - 2) + 5x

8x - 20 - 9x - 3 = - 6x + 12 + 5x

8x - 9x + 6x - 5x = 12 + 20 + 3

0x = 35

f) 3 (2x - 5) - (4x + 7) = 5 (2x - 1)-(3x + 1)

6x - 15 - 4x - 7 = 10x - 5 - 3x - 1

6x - 4x - 10x + 3x = - 5 - 1 + 15 + 7

- 5x = 16.

x = - 16/5.