Chapter 8.5, Problem 88E

The graph shows stopping distances for trucks at various speeds on dry roads and on wet roads. Use this information to solve Exercises 88–89.

a. Use the statistical menu of your graphing utility and the quadratic regression program to obtain the quadratic function that models a truck’s stopping distance, $f(x)$, in feet, on dry pavement travelling at $x$ miles per hour. Round the constant term to one decimal place.

b. Use the function from part (a) to determine speeds on dry pavement requiring stopping distances that exceed 455 feet. Round to the nearest mile per hour.