a. The rocket takes 4 seconds to reach maximum height, and the maximum height is 400 ft.
b. 2 and 3
Question 5:
In the formula, h(t)=400-16(t-4)^{2}, the 400 represents it's maximum height and the -4 represents the amount of seconds it takes to reach that height because, since t is the seconds, subtracting 4 means that that is the amount of seconds it takes.
Question 6:
It's asking the x values for the points that are on the y-axis. Simply flip the negatives into positives on the (x-2) and (x-3). You'll get 2 and 3.
For additional help, you could go to Desmos Graphing Calculator and enter the equation and it'll give you a visual representation of the graph. It helps a lot!
Anything else?? :D