Update/downdate of a dense Cholesky factorization</a></li>
               <li><a href="#19">Caveat Executor</a></li>
               <li><a href="#20">Summary</a></li>
            </ul>
         </div>
         <h2>Rule Number One: never multiply by the inverse, inv(A)<a name="1"></a></h2>
         <p>Use backslash or a matrix factorization instead (LU, CHOL, or QR).</p>
         <h2>Rule Number Two:  never break Rule Number One<a name="2"></a></h2>
         <p>However, the problem with Rule Number One is th