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1 )   5 x - 15 - 3 x + 7 = 2 x - 8

2 )   5 x - 15 - 3 x + 7 =  9

       2 x - 8 =  9

       2 x = 9 + 8

       2 x = 17

              x = 17/2

1  )  2 x - 14

     - 3 x + 3

2 x - 14 = - 3 x + 3

2 x +  3x = 3 + 14

5 x = 17

x = 17/5

42 - 14 x - 12 x - 3 = 0

- 26 x =  - 42 + 3

- 26 x = - 39

x =  39/26  = 3/2

Réponse:

Exercice 3:

1) 5(x-3) -3x +7 = 5x-15-3x+7= 2x - 8

2) 2x-8 = 9 , 2x-8-9= 0 soit 2x-17=0 , x= 17/2

Exercice 4:

1) 2(x-7)= 2x -14 et 3(-x+1) = -3x +3

2)

2x-14 = -3x +3

5x = 17

x= 17/5

Exercice 5:

1)

7(6-2x) - 3 (4x+1) = 0

(42 - 14x) - ( 12x +3) = 0

42 -14x -12x -3 =0

-26x + 39 = 0

-26x= -39

x= 39/26

x= 1.5