%matplotlib inline
import pylab as plt
from numpy import *

def cuberoot(x):  # facilitate taking cube root of negative numbers
    return sign(x)*abs(x)**(1./3)

cvals = linspace(-2,2,30)**3  # cube it to concentrate around 0
r = 2
t = linspace(-r,r,500)
for c in cvals:
    plt.plot( t, cuberoot(1.5*t**2+c),'k',alpha=0.25 )
#plt.axis('off');