Bonsoir vous pouvez m’aidez à faire l’exercice 18,19 svp

bonjour

18

f (1) = - 1

f ( - 2) = - 7

( - 7 + 1) / ( - 2 - 1 ) = - 6 / - 3 = 2

la fonction est du type ax + b

f (1) = - 1

1 * 2 + b = - 1

→ b = - 1 - 2 = - 3

f(x) = 2 x - 3

f ( -2 ) = - 7

- 2 * 2 - 3 = - 4 - 3 = - 7

2)   f ( - 1 )= 1

    f ( - 7 ) = - 2

( - 2 - 1 ) : ( - 7 + 1) = - 3 / - 6 = 1/2 = 0.5

f ( -1)  = 1

- 1 * 0.5 + b = 1  → b = 1 + 0.5 = 1.5

f( x) = 0.5 x + 1.5

on vérifie  : f ( - 7) = - 7 * 0.5 + 1.5 = - 3.5 + 1.5 =  - 2

19)

f ( 2) = - 1 et f ( - 1) = 5

( 5 + 1 ) / ( - 1 - 2 ) = 6/-3 = - 2

2 * - 2 + b = - 1 → b = - 1 + 4 = 3

f (x) = - 2 x + 3

on vérifie

f ( - 1 ) = 5

- 1 * - 2 + 3 = 2 + 3 = 5