import matplotlib.pyplot as plt
import numpy as np
x=np.linspace(-3,3,50)
y1=2*x+1
y2=x**2
plt.figure()
plt.plot(x,y1)
plt.figure(num=3,figsize=(8,5))
plt.plot(x,y2)
plt.plot(x,y1,color='red',linewidth=1.0,linestyle='--')
plt.show()

