#%% Import of packages

import matplotlib.pyplot as plt
import numpy as np

#%% Function f(x)

def fun_f(x):
    f = (x + 1)*(x - 1)   
    return f

#%% Generating x_array

x_low = -2
x_high = 2
dx = 0.1
x_array = np.arange(x_low, x_high+dx, dx)
 
#%% Function values

f_array = fun_f(x_array)

#%% Plotting

plt.close('all')
plt.figure(1)

plt.plot(x_array, f_array, 'b', label='f(x)')
plt.plot(-1, 0, 'ro')
plt.plot(1, 0, 'ro')
plt.legend()
plt.grid()
plt.xlabel('x')
plt.ylabel('f(x)')

plt.savefig('plot_f_secorder.pdf')  # pdf of plot
plt.show()