bonjour
C (x) = x ³ - 25 x² + 280 x + 400
R (x) = 480 x - 20 x²
B (x) = - 20 x² + 480 x - ( x ³ - 25 x² + 280 x + 400 )
B (x) = - 20 x² + 480 x - x³ + 25 x² - 280 x - 400
B (x) = - x ³ + 5 x² + 200 x - 400
B ' (x) = - 3 x² + 10 x + 200
- 3 x² + 10 x + 200 = 0
Δ = 100 - 4 ( - 3 *200 ) = 100 + 2 400 = 2 500 = 50²
x 1 = ( - 10 + 50 ) / - 6 = - 40/6
x 2 = ( - 10 - 50 ) / - 6 = 60/6 = 10
Bénéfice maximal pour 10 portables / jour
