Раскрытие скобок a+(-3b+2c). -x-(-3p-2y). -(m-2n)+(-3a+b). (x-5)-(7-x)+(9-x). -4,5+(-5,6+4,5). -4,5-(-5,6-4,5)

Question

Алгебра: Раскрытие скобок a+(-3b+2c). -x-(-3p-2y). -(m-2n)+(-3a+b). (x-5)-(7-x)+(9-x). -4,5+(-5,6+4,5). -4,5-(-5,6-4,5)

fgydsgfgysa · Accepted Answer

Cos4x -sin2x =0 ; x ∈ [ 0 ;π] .

1 -2sin²2x - sin2x =0 ⇔2sin²2x +sin2x -1 =0 ⇒ [ sin2x = -1 ; sin2x =1/2.
[ 2x = -π/2 +2πn ; 2x = π/6 + 2πn ; 2x = 5π/6 + 2πn , n∈ Z.⇔
[ x = -π/4 +πn ; x = π/12 + πn ; x = 5π/12 + πn , n∈ Z.

ответ:   { π/12 ; 5π/12 ; 3π/4} .
* * * * * * *
a) 0≤ -π/4 + πn ≤ π  ⇔ π/4 ≤  πn ≤ 5 π/4 ⇔1/4 ≤  n ≤ 5 /4 ⇒ n = 1.
решение: -π/4 + π =3π/4 .
b)    0≤  π/12 + πn  ≤ π ⇔ - π/12 ≤ πn ≤ π - π/12⇔-1/12 ≤ n ≤ 11/12 ⇒ n =0.
решение: π/12 + πn = π/12.
c) 0 ≤5π/12 + πn ≤ π ⇔ - 5π/12 ≤ πn ≤ π- 5π/12⇔ -5/12  ≤ n ≤ 71/12⇒ n =0
решение: 5π/12 + πn=  5π/12  .

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