Solving a cubic equation in Python using fsolve - only one root is obtained

I am trying to solve a cubic equation in Python. However I am getting only one root of the equation. Please find the code snippet below.

import numpy as np

from scipy import optimize as op

def my_func(p):

k = 0.17
d = 3e-6
A = 1.6e-9
epsilon = 8.85e-12
Vspi = np.sqrt((8*k*np.power(d,3))/(27*epsilon*A))

Vdc = 0.2 * Vspi

xeq = p
F = (k*np.power(xeq,3))-(2*k*d*np.power(xeq,2))+(2*k*np.power(d,2)*xeq)-(epsilon*A*np.power(Vdc,2))
return F

zguess = 0.5e-6

z = op.fsolve(my_func,zguess)

print(z)


What is the mistake ? I am supposed to obtain three roots.

Regards, Raghu