Bonjour,
f(x) = 2x² - 4x + 13
f'(x) = 4x - 4
On pose f'(x) = 0 ⇔ 4x - 4 = 0 ⇔ 4x = 4 ⇔ x = 4/4 = 1
Tableau de variation :
x |-∞ 1 +∞
f'(x) | - 0 +
f(x) | ↘ ↗
g(x) = 3x² + 15x - 4
g'(x) = 6x + 15
On pose g'(x) = 0 ⇔ 6x + 15 = 0 ⇔ 6x = -15 ⇔ x = -15/6 = (-5 × 3)/(3 × 2) = -5/2
Tableau de variation :
x |-∞ -5/2 +∞
f'(x) | - 0 +
f(x) | ↘ ↗
