-x² - 17x - 72 ≥ 0
x² + 17x + 72 ≤ 0 D = b²-4ac = 289-288 = 1
x₁₂ = (-b±√D)/2a
x₁ = (-17+1)/2 = -8
x₂ = (-17-1)/2 = -9
(x + 8)(x + 9) ≤ 0
x ≤ -8
x ≥ -9
ответ: x ∈ [-9; -8]
-x² - 17x - 72 ≥ 0
x² + 17x + 72 ≤ 0 D = b²-4ac = 289-288 = 1
x₁₂ = (-b±√D)/2a
x₁ = (-17+1)/2 = -8
x₂ = (-17-1)/2 = -9
(x + 8)(x + 9) ≤ 0
x ≤ -8
x ≥ -9
ответ: x ∈ [-9; -8]