How does a quadratic function relate to volleyball and what aspects of quadratic functions are there?

Volleyball players want to keep their serves as close to the net as possible, so the ball travels for a shorter period of time. Say a volleyball player serves the ball across the court. If we can model this situation with the function y=-0.006(x−21)2+9, where x is the distance from the player and y is the height, then we can determine if the ball clears the net and lands in bounds 61 feet away1. It may be helpful to analyze this situation graphically, and we consider how to do that in this section.    

Step-by-step explanation:

nope

none of the above.

for one of the equations to be used in the process, there has to be a term in the equation since squared is .

since there is only a term in the first equation, we cannot derive a from completing the square.

solving with completing the square