Chapter 2.5, Problem 29E

Wind chill The table gives the wind chill temperature when the outside temperature is ${20}^{o}F$.

$\begin{array}{llll}\text{Wind}\hfill & \text{WindChill}\hfill & \text{Wind}\hfill & \text{WindChill}\hfill \\ \text{(mph)}\hfill & {\text{(}}^{\text{o}}\text{F)}\hfill & \text{(mph)}\hfill & {\text{(}}^{\text{o}}\text{F)}\hfill \\ \text{5}\hfill & \text{13}\hfill & \text{35}\hfill & \text{0}\hfill \\ \text{10}\hfill & \text{9}\hfill & \text{40}\hfill & \text{-1}\hfill \\ \text{15}\hfill & \text{6}\hfill & \text{45}\hfill & \text{-2}\hfill \\ \text{20}\hfill & \text{4}\hfill & \text{50}\hfill & \text{-3}\hfill \\ \text{25}\hfill & \text{3}\hfill & \text{55}\hfill & \text{-3}\hfill \\ \text{30}\hfill & \text{1}\hfill & \text{60}\hfill & \text{-4}\hfill \end{array}$

Use $x$ as the wind speed and create q quadratic model for these data.

At what wind speed does the model predict that the wind chill temperature will be lowest?

Do you think the model found in part (a) is valid for $x>60$? Explain.