 class="problem">
    Compute the product $\begin{bmatrix}3 &amp; 2&amp; 1\\ 0 &amp;
    1&amp; -4\end{bmatrix}
    \begin{bmatrix}      -1&amp;3 &amp;0 \\ 2&amp;-1 &amp;0\\ 0&amp;1 &amp;2\end{bmatrix}$.
  </div>

<section>  <h1>Determinants</h1>

  <p>Associated with every square matrix is a number, called the
  <em>determinant</em>, which is related to length, area, and volume.
  We'll use the determinant to generalize the concept of volume to
  higher dimensions as well.  Determinants will appear as we s