bonjour
1) tableau de valeurs
(voir fichier joint
2)
f(x) = 4x³ -120x² +900x
dérivée de f(x) :
4 × 3 × x^(3-1) - 2 × 120 × x^(2-1) + 900
=12x² -240x+ 900
3)
résoudre f'(x) = 0
df = [2;8]
12x² -240x+900 =0
delta
= b²-4ac
= (-240)² - (4×12×900)
=14400
=120²
x1 = -b-√Δ/2a
=(240-120)/(12×2)
=120/24
=5
x2 = -b+√Δ/2a
=(240+120) /(12×2)
=360/24
=15
solution ={ 5;15}
4)
f'(6)
=12×(6)² -240×(6)+900
= 432-1440+900
= -108
