$$\begin{array}{l}{\text { Approximating a Derivative In Exercises } 67 \text { and } 68 \text { , }} \\ {\text { evaluate } f(2) \text { and } f(2.1) \text { and use the results to approximate } f^{\prime}(2) \text { . }}\end{array}$$
$$f(x)=x(4-x)$$