import numpy as np
import matplotlib.pyplot as plt
import sys

formula = sys.argv[1]
xmin = float(sys.argv[2])
xmax = float(sys.argv[3])

x = np.linspace(xmin, xmax, 101)
y = eval(formula)
plt.plot(x, y)
plt.title(formula)
plt.show()

"""
Terminal> plotf.py "x**2 -3*x +1" -3 3
"""