Минимум функции

import numpy as np
import matplotlib.pyplot as plt


import scipy.interpolate
import scipy.integrate
from scipy.optimize import minimize

def func(x):
    y=3*x*x+2*x
    return y

print func(4)

def minimize_own(x):
    dx=0.1
    eps=1e-6
    x0=5
    while (dx > eps):
        f_left =func(x0- dx)
        f_right = func(x0+ dx)
        f_midle = func(x0)
        if (f_left< f_midle):
            x0=x0-dx
        elif(f_right< f_midle):
            x0=x0+dx
        else:
            dx*=0.5
        print x0,dx


#print minimize(3)
res = minimize(func, (5))
print res.x
xar=np.arange(-10,10,0.01)
plt.plot(xar, func(xar))
plt.show()