y to express matrix multiplication without
      having to introduce matrices.</span><span class=
      "larsonfive">See Larson 13.5:7&ndash;10 for more practice.</span>
    </div>
      
      Complete the following:

    <ol>
      <li>Suppose that $w=f(x,y,z)$ and that $x,y,z$ are all
      function of one variable $t$ (so $x=g(t), y=h(t), z=k(t)$).
      Use the chain rule with matrix multiplication to explain why
      $$\frac{dw}{dt} = \frac{\partial f}{\partial
      x}\frac{dg}{dt}+\frac{\partial f}