Question

tennis ball thrown upwards from the top of a 30ft high building. It's height, in feet above the ground, t-seconds after it is thrown is given by H=-16t^2+80t+30 algerbraiclly determine the time when the ball reaches its greatest height and what is the height?

Answer 1

Another way of thinking about its "highest point" is by thinking about the vertex. The time of the vertex is defined as t = b/2a (if the equation is of the form at^2+bt+c)

which is, t = 2.5
Then, plug this into the equation to find -16(2.5)^2+80(2.5)+30 = 130.