title: How do I use lhs and rhs to define a function?
body: <p>In the Maxima session below, how come <em>f</em>(1) is not 0?</p>
  
  <pre><code>(%i1) eq: 2 * x + 1 = 3;
  (%o1)                             2 x + 1 = 3
  (%i2) f(x) := lhs(eq) - rhs(eq);
  (%o2)                      f(x) := lhs(eq) - rhs(eq)
  (%i3) f(1);
  (%o3)                               2 x - 2
  </code></pre>