Let f(z)=z+z4. Use the the Leau-Fatou flower theorem to find (weakly) attracting and repulsive directions for the neutral fixed point at the origin.
A simple neutral fixed point problem


Note n=3 and a=1. Suppose navn=3v3=1 Then v=(1/3)1/3=3−1/3(e2kπi)1/3=3−1/3e2kπi/3,k=0,1,2,3,⋯ but there exist unique values of v only for k=0,1,2. To get the repulsive directions, substitute our values of k into the exponential term and simplify. f is repulsive in the directions 1, −1/2+i√3/2, and −1/2−i√3/2.
Suppose instead that navn=3v3=−1 Then v=(−1/3)1/3=3−1/3(e(2k+1)πi)1/3=3−1/3e(2k+1)πi/3,k=0,1,2,3,⋯ but there exist unique values of v only for k=0,1,2. To get the attractive directions, substitute our values of k into the exponential term and simplify. f is attractive in the directions −1/2+i√3/2, −1, and 1/2−i√3/2.

This looks good. Here's an image of the Julia set with the weakly attractive and repulsive vectors shown:

This all makes sense to me, but can you explain exactly how you are plugging in the values of k into the exponential term and simplifying?

@Yousername
RedCrayon is using the fact that
eiθ=cos(θ)+isin(θ).
Thus, for example,
eiπ/3=cos(π/3)+isin(π/3)=12+i√32.
Keep in mind that, for an equation like vn=1, we expect n solutions equally spaced about the unit circle.