title: I know the range of functions, but I can't draw a graph
body: <p>I know the range of functions, but I can't draw a graph. I tried to plot an expression of <code>5x^2 - 4xy + 2y^2 = 30</code> in y form. And, the results are as follows:</p>
  
  <p><code>y = ±sqrt((240 - 24 x^2)/4) + x (x ≤ 10^(1/2) , x ≥ -10^(1/2)</code> </p>
  
  <p>I'd like to draw a graph called y, but the range is given as above. I don't know how to set ranges like <code>x ≤ 10^ (1/2)</code>, and if you know how to graph more efficiently than this, please advise. The code below is the code I've written so far:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  x = np.linspace(-10,10,1000000)
  c = np.sqrt((240 - 24 * x ** 2) / 4) + x
  
  y = c
  y1 = - c
  
  plt.plot(x, y ,'r')
  plt.plot(x, y1, 'b')
  plt.ylim(-10,10)
  plt.xlim(-10,10)
  plt.grid()
  plt.xlabel('x')
  plt.ylabel('i')
  plt.show()
  </code></pre>
  
  <p>I thought this would draw a graph, but it won't.</p>