bonjour
C (x) = x² + 50 x + 400
R (x) = 100 x
B (x) = 100 x - ( x² + 50 x + 400 ) = 100 x - x² - 50 x - 400 = - x² + 50 x - 400
- x² + 50 x - 400 = 0
Δ = 50² - 4 ( - 1 * -400 ) = 2 500 - 1 600 = 900 = 30 ²
x 1 = ( - 50 - 30 ) / - 2 = - 80 /- 2 = 40
x 2 = ( - 50 + 30 ) / - 2 = - 20 / - 2 = 10