cos 2x•cosx - sin2x•sinx = 0
cos2x•cosx - 2cosx•sin²x = 0
cosx(cos2x-2sin²x)= 0
cosx(cos2x-1+cos2x)= 0
cosx(2cos2x-1) = 0
1)cos x = 0
x = π/2 + πn, n€Z
2)2cos2x = 1
cos2x = 1/2
2x = ±π/3 + 2πk
x = ±π/6 + πk, k€Z
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Правильный ответ с) ах(4) + bx(2) + с = 0.
Удачи)))
Log(4)192-log(4)3 =log(4)(192/3)=log(4)64=3