title: how to add expressions and do numerical calculation in Maxima?
body: <p>I would like to ask:</p>
  
  <ol>
  <li><p>how I can add expressions in Maxima? i.e. I have:</p>
  
  <pre><code>A = x + y;
  B = 2*x + 2*y;
  </code></pre>
  
  <p><strong>How to get <code>Maxima</code> to give me <code>(A + B)</code>?</strong></p></li>
  <li><p>how I can do numerical calculation in Maxima?  I want to assign</p>
  
  <pre><code>x = 1;
  b = 2;
  </code></pre>
  
  <p><strong>How to get the numerical value of <code>(A + B)</code>?</strong></p></li>
  </ol>