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  • Utilisateur Brainly
2014-05-17T16:28:21+02:00

Exercice 10 :

a . 5x-2 = -7

5x = -7 + 2= -5

x = -5 / 5 = -1

Si x = -1 alors 5 * (-1) -2 = -7

Donc -5 -2 = -7

Donc -7 = -7


b. 9x - 64 = -1

9x = -1 + 64 = 63

x = 63 / 9 = 7

Si x= 7 alors 9*7 - 64 = -1

Donc 63 -64 = -1

Donc -1 = -1


Exercice 11 :

a . 3x + 2 = x + 6

3x - x + 2 = 6

2x = 6-2 = 4

x = 4/2= 2

Si x = 2 alors 3*2 +2 = 2 + 6

Donc 6 + 2 = 2 + 6

Donc 8 = 8


b. -8x + 3 = 5x -2

3 = 5x + 8x -2

3 + 2 = 13x

5 = 13 x

Donc x = 5/13

Si x = 5/13 alors -8 * 5/13 + 3 = 5* 5/13 -2

-40/13 + 3 = 25 /13 -2

-40/13 + 39/13 = 25 /13 - 26 / 13

-1/13 = -1/13