Question

4sin^2 x + 5sin x < 0

Answer 1

4sin²x + 5sinx < 0

sinx(4sinx + 5) < 0

Найдем нули:

sinx = 0

4sinx + 5 = 0

sinx = -5/4 -- не удовл., т.к. -1 ≤ sinx ≤ 1

=> sinx < 0

x ∈ (π + 2πn; 2π + 2πn)

Answer 2

Решите пример
6*(1/3)² - 8*1/3 = ?
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