J'suis pas certaine non plus mais voici.
1)
R(x) = prix * quantité
R(x) = 50x
2)
x = 50
C(50) = x² - 10x + 500
C(50) = x² - 10*50 + 500
C(50) = 2 500
R(50) = 50x
R(50) = 2 500
B(x) = R(x) - C(x)
B(50) = 2 500 - 2 500 = 0
3)
B(x) = - x² + 60x - 500
B(50) = - 2 500 + 60*50 - 500
B(50) = - 2 500 + 3 000 - 500
B(50) = 0
4)
a. - (x - 30)² + 400 = - (x² - 2*30*x + 30²) + 400 = -x² + 60x - 900 + 400 = -x² + 60x - 500 = B(x)
