arccos 1+2x/3=2П/3 решить

arccos (1+2x/3)=2π/3

arccos(1+2x/3)=2π/3, x∈[-3,0]

1+2x/3=cos(2π/3)

1+2x/3=-1/2

6+4x=-3

4x=-3-6

4x=-9

x=-9/4, x∈ [-3,0]