f(x)=x3+27=(x+3)(x2-3x+9).
x2-3x=-9 satisfies the quadratic,
x2-3x+9/4=-9+9/4=-27/4,
(x-3/2)2=-27/4, x-3/2=±√(-27/4)=±½3i√3.
The real zero is -3, and the complex zeroes are 3/2+½3i√3 and 3/2-½3i√3.
The complex zeroes could be written: (3/2)(1+i√3) and (3/2)(1-i√3).