f ' ( x ) = 4x³ -12x + 27
f ' ' ( x) =12x² -12 = 12 · ( x² - 1 )
CONCAVA , CONVEXA = derivata a doua cu TABEL = radacini si SEMN
x ∈ R ↓
f '' (x ) = 0
x² - 1 =0 ⇒ x₁ = -1 ; x₂ = 1
rad. deriv. II
x -∞ - 1 1 +∞
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f ''(x) + + 0 - 0 + + + + SEMN din f'' =12(x² - 1 )
↓ ↓ ↓
f este convexa concava convexa
