input: Write a python function to plot two linear equations using matplotlib.
  assert plot_linear_equations([-10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 
                               [5*i + 2 for i in range(-10, 10)], 
                               [-3*i + 6 for i in range(-10, 10)]) == None
output: import matplotlib.pyplot as plt
  
  def plot_linear_equations(x_values, y1_values, y2_values):
      plt.plot(x_values, y1_values, label='y = 5x + 2')
      plt.plot(x_values, y2_values, label='y = -3x + 6')
      
      plt.xlabel('x')
      plt.ylabel('y')
      plt.title('Plot of two linear equations')
      plt.legend()
      
      plt.grid(True)
      plt.show()