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?

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.