The distance d (in feet) that it

takes a car to come to a complete stop can be modeled

by d = 0.05s^2 + 2.2s, where s is the speed of the car

(in miles per hour). A car has 168 feet to come to a

complete stop. Find the maximum speed at which the

car can travel.

40 mph

Step-by-step explanation:

To find the maximum speed at which the car can travel, as the distance it requires to stop is 168 feet, we just need to use the value of d = 168 in the equation, and then find the value of s:

168 = 0.05s^2 + 2.2s

0.05s^2 + 2.2s - 168 = 0

Using Bhaskara's formula: we have:

Delta = 2.2^2 + 4*0.05*168 = 38.44

sqrt (Delta) = 6.2

s1 = (-2.2 + 6.2) / 0.1 = 40 mph

s2 = (-2.2 - 6.2) / 0.1 = - 84 mph (a negative value does not make sense as 's' is the speed of the car)

So the maximum speed of the car is 40 mph