Я исправил ошибку. вот теперь правильно
Там просто раскрывает формулу и дальше дискриминантом.
64х^3+144х^2+108х+27=0
64х^3+48х^2+96х^2+72х+36х+27=0
16х^2*(4х+3)+24х*(4х+3)+9*(4х+3)=0
(4х+3)*(16х^2+24х+9)=0
(4х+3)*(4х+3)^2=0
(4х+3)^3=0
4х+3=0
4х=-3
х=-3/4=-0,75
(cos 7x -cos3x) +(sin8x+sin2x) =0;
- 2sin2xsin5x +2sin5xcos3x = 0;
sin5x(sin2x -cos3x) =0 ;
sin5x=0 ⇒ x =π*k/5 ,k ∈Z .
sin2x -cos3x =0
sin2x -sin(π/2 -3x) =0;
2sin(5x/2 -π/4)*cos(π/4 -x/2) =0 ;
sin(5x/2 -π/4)*cos(x/2 -π/4 ) =0 ;
sin(5x/2 -π/4) =0⇒5x/2 -π/4 =π*k ⇔ x = π/10+2π/5*k,k ∈Z
cos(x/2 -π/4)= 0 ⇒x/2 - π/4 =π/2 +π*k ⇔ x=3π/2+2π*k ,k∈Z
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<em>sin2x -cos3x=0;</em>
<em>2sinxcosx -cosx(4cos²x -3) =0;²</em>
<em>cosx(2sinx -4cos²x +3) =0</em>
<em>cosx(4sin²x +2sinx -1) =0</em>