bonjour

f (x) = 2 x + 6

2 x + 6  = 2

2 x = 2 - 6

2 x = - 4

x = - 2

f ( - 2) = 2

2 x + 6 = 0

2 x = - 6

x = - 3

f (  - 3) = 0

2 x + 6  = 15/2

4 x /2 + 12/2 = 15/2

4 x  = 15- 12

4 x = 3

x = 3 /4  

f ( 3/4) = 15/2