AFDA Quadratic equation problem

Question

Culkin hall is approximately 64 feet high. Suppose you are standing on top of the building and decide to toss a book in the air. The distance of this book above the ground (in feet) as a function of time (in seconds) is given by s(t) = -16² +48t+64.

a. When the book hits the ground, what is the value of t?

b. What is the maximum height that the book attains?

Answer 1

a. Solve s(t)=0.

b.As in the previous problem: the maximum point of the quadratic equation Ax² + Bx + C occurs when x = -B/2A.

Answer 2

This can also be written as s(t)=16(-t²+3t +4)=-16(t²-3t-4)=-16(t-4)(t+1)

This has zeros at t=4 and t=-1. So the book hits the ground in 4 seconds/ It reaches an apex at t=3/2. At that time the object will be -16((3/2 -4)(3/2+1)= -16*(-6.25) you can do the rest.