Réponse :

Explications étape par étape :

exercice 29

a)

7 x + 15 =  6 x + 3

7 x - 6 x= 3 - 15

x = - 12

b)

(-1/3) x + 3 = (2/3) x - 2

3 + 2 = (2/3) x + (-1/3) x

5 = (2/3) x - (1/3) x

5 = (1/3) x

15 = x

c)

3,2 + 8 x = 9 x - 5,1

3,2 + 5,1  = 9 x - 8 x

8,3 = x

d)

0,9 x - 4 = - 0,1 x - 6

0,9 x + 0,1 x = - 6 + 4

x = - 2

exercice 30

a)

12 x + 15 = 6 x + 3

12 x - 6 x = 3 - 15

6 x = - 12

x = - 12/6

x = - 2

b)

5 x - 3 = 2 x + 4

5 x - 2 x = 4 + 3

3 x = 7

x = 7/3

c)

- 7 x - 8 =  - 10 x + 4

- 7 x + 10 x = 4 + 8

3 x = 12

x = 12/

x = 4

d)

2 x + 7 = 9 x - 5

7 + 5 = 9 x - 2 x

12 = 7 x

12/7 = x