Pouvez vous résoudre mes exercices svp

bonsoir

f ( 7 ) = 2.8 et  f( 10 ) = 3

( 3 - 2.8 ) / ( 10 - 7 ) = 0.2 / 3  = 2 /30 = 1 /15

ax = x /15

f ( 10 ) =  3

10*1/15 + b = 3

b = 3 - 10/15 =  45/15 - 10 /15 = 35/15  = 7 /3

f(x) = x /15 + 7/3

d'où  f ( 7) = 7 * 1/15 + 7/3 = 7/15 + 35/15 = 42/15 = 2.8

f ( 15 ) = 5

f (x) =  5x /15 = x / 3

f ( - 3 ) = - 3 /3 = - 1

f ( 2/5) =  2/5 x 1/3 = 2 /15

x /3 = 2

x = 6

x /2 = - 9

x = - 18