title: Can O(N+NM) be simplified to O(NM)?
body: <p>Suppose that <code>N</code> and <code>M</code> are two parameters of an algorithm. Is the following simplification correct?</p>
  
  <pre><code>O(N+NM) = O[N(1+M)] = O(NM)
  </code></pre>
  
  <p>In other words, is it allowed to remove the constant in such a context?</p>