title: Convert an equation system to matrix form in Maxima
body: <p>I have an equation system on the form:</p>
  
  <pre><code>eq1 : q = a*x+b*y;
  eq2 : r = c*x+d*y;
  </code></pre>
  
  <p>I would like it to get the coefficient matrix, which in this simple case is:</p>
  
  <pre><code>T : matrix([a,b], [c,d]);
  </code></pre>
  
  <p>So that I can express the equation system as:</p>
  
  <pre><code>eq3 : Q = T . X;
  </code></pre>
  
  <p>Because I want to use <code>T</code> in further matrix operations.
  (The original equations are what I get from my problem and I don't want to turn them into matrix form manually, as that's what this kind of program is for. But I just can't figure it out)</p>