Verified answer

везде метод интервалов

3.

2x² - 16 < 0

x² - 8 < 0

(x - √8)(x + √8) < 0

-++++++++++(-√8) -------------------------- (√8) +++++++++++++

x∈ (-√8, √8)

4

x³ - 9x ≥ 0

x(x² - 9) ≥ 0

x(x - 3)(x + 3) ≥ 0

------------[-3] ++++++++ [0] ----------- [3] +++++++++

x ∈ [-3, 0] U [3, +∞)

6

(x² - 25)/(x² + 9x + 8) > 0

(x - 5)(x + 5)/(x + 1)(x + 8) > 0

-+++++++(-8) ---------- (-5) +++++++ (-1) -------------(5) +++++++++

x ∈ (-∞, -8) U (-5, 1) U (5, +∞)