$ remain constant, what is $dV/dt$? Use
      this to find a formula for $dV$ in terms of $dx$, assuming
      that $y$ and $z$ are constant.</li>

      <li>Repeat the last step for when $y$ is the only variable
      that changes, and then for when $z$ is the only variable that
      changes.</li>

      <li>What is $dV/dt$ in terms of $dx/dt$, $dy/dt$, and $dz/dt$
      when all three variables are changing? Solve for $dV$.</li>

      <li>
        
          Show that we can write $dV$ as the matrix pro