bonjour
f (7) = - 3 et f ( 10 ) = 0
( 0 + 3 ) / ( 10 - 7 ) = 3/3 = 1 donc ax = x
f ( 7) = - 3
7 * 1 + b = - 3
b = - 3 - 7 = - 10
donc f (x) = x - 10
d'où f ( 10 ) = 10 - 10 = 0
f ( - 1 ) = - 1 - 10 = - 11
10 a pour image 0
15 a pour image 6
f (5) = 5 - 10 = - 5