Réponse :

bonjour

f (0) = 0 et  f ( 2) = 3

(  3 - 0 ) / ( 2 - 0 ) =  3/2

ax = 3 x /2

f (2) =  3

 2 * 3 /2 + b = 3

 6/2 + b   = 3

  b = 3 - 3 = 0

f (x) = 3 x /2 + 0

f ( 0 ) = 4 et  f ( 4 ) = 0

( 0 - 4 ) / ( 4 - 0 ) = - 4 /4 = - 1

ax =  - x

f ( 0 ) =  4

0 + b = 4  donc  b = 4

f (x) = - x + 4

d'où  f ( 4 ) = - 4 + 4 = 0

continue