Cosx=y
2y^2+y-1=0
D=√9
y=-1
y=0.5
cosx=-1
x=π+2πn
cosx=0.5
x=+-arccos0.5+2πn
x=+-π/3+2πn
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207 * 193 = (200 + 7)(200 - 7) = 200² - 7²
9 - 6x < 0
4x > 0
9 > 6x
x > 0
x < 9:6
x > 0
x < 1,5
x > 0
Ответ: x ∈ (0; 1,5).