f(x)=2x³ + 3x² -12x +7
f'(x) = 6x² + 6x - 12
6x² + 6x - 12 = 0
x² + x - 2 = 0
D = 9
x₁ = -2
x₂ = 1
при x ∈ (-∞; -2) f'(x) > 0, f(x)↑
при х = -2 f'(x) = 0, f(x) = 27, max
при х ∈ (-2; 1) f'(x) < 0, f(x)↓
при х = 1 f'(x) = 0, f(x) = 1, min
при х ∈ (1; ∞) f'(x) > 0, f(x)↑