Réponse :
bonjour
f (5) = - 1 et f( 15 ) = - 9
( - 9 + 1 ) / ( 15 - 5 ) = - 8/10 = - 4/5
ax = - 4 x /5
f (5) = - 1
5 * - 4/5 + b = - 1
- 20 /5 + b = - 1
- 4 + b = - 1
b = - 1 + 4 = 3
f (x) = - 4 x / 5 + 3
f ( 15 )= 15 * - 4/5 + 3 = - 60/5 + 3 = - 9
f ( 25) = 25 * - 4/5 + 3 = - 100/5 + 3 = - 17
Explications étape par étape
