Okay, so this question is asking you about a graph (h(t)=-t^2+4t). Because of the -t^2 this will be a parabola that opens downwards. h(t)=-t^2+4t, you can find that the graph will start at zero (since there is no starting value). The easiest way for you to solve this would be if you had a graphing calculator, if you don't then just use an online graphing website. This is a quadratic problem, so they are constructed as AT^2+BT+C, in this problem A=-1,B=4,C=0. To find the vertex, do -(B/2A), which will give you the X value (T value in this case) of the vertex, then you plug that into your graphing toll, and that gives you the vertex. To find the average rate of change between t=2.5 and t=3, you need to find their Y values. Then you find the difference between those values, and multiply it by two, (since their space is 0.5), and that is your AROC (average rate of change). This means that this is the approximated change rate for the graph since it is inconsistent. Hope this helps explain :D
