a)
tarif a = 21 + ( 1.5 x 8) = 33 euros
tarif b = 8 x 5 = 40 euros
b)
tarif A
f(x) = 1.5 x + 21
tarif B
f(x) = 5 x
c)
1.5x + 21 = 5x
21 = 5x - 1.5x
21 = 3.5 x
x = 21/3.5 = 6
pour 6 seances le tarif a et b seront égaux
je vérifie
si x=6
tarifA = 6 x 1.5 + 21 = 30 euros
tarif b = 6 x 5 = 30 euros
