Réponses

  • Omnes
  • Modérateur confirmé
2014-03-27T23:59:56+01:00
Salut,

f(1) = 1, f(3) = -3

a =  \frac{f(3) - f(1) }{3-1} =  \frac{-3 -1}{3-1} =  \frac{-4}{2} = -2

On a donc f(x) = -2x + b

f(1) = -2 + b
-2 + b = 1
b = 1+2
b = 3

On a donc f(x) = -2x + 3.

On vérifie :

f(3) = -2*3 + 3 = -6 + 3 = -3
f(1) = -2*1 + 3 = -2 + 3 = 1

Bonne soirée !