Question

The stopping distance D in feet for a car traveling at x miles per hour is given by d(x)= (1/12)x^2+(11/9)x. Determine the driving speeds that correspond to stopping distances between 300 and 500 feet, inclusive. Round speeds to the nearest mile per hour.

Answer 1

x^2/12 + 11x/9 = 300
Multiply both sides by 36:
3x^2 + 44x = 10800
3x^2 + 44x - 10800 = 0
Use Quadratic Formula:
X = 53.1 mi/h.

Answer 2

the distance d in feel that it take s an automobile to stop if it is traveling S miles per hour is given by:
S=21d
Find the distance it would take an automobile traveling 60mph to stop.

Answer 3

The stopping distance d in feet for a car traveling at speed of s miles per hour depends on car road conditions. here are two possible stopping distance formulas: d=3s and d=0.05s^2+s. Write and solve an equation to answer the question, "for what speed(s) do the two function predict the same stopping distance