Answer:
A function to represent the height of the ball in terms of its distance from the player's hands is 
Step-by-step explanation:
General equation of parabola in vertex form 
y represents the height
x represents horizontal distance 
(h,k) is the coordinates of vertex of parabola 
We are given that The  ball travels to a maximum height of 12 feet when it is a horizontal distance of 18 feet from the player's hands.
So,(h,k)=(18,12)
Substitute the value in equation 
  ---1
The ball leaves the player's hands at a height of 6 feet above the ground and the distance at this time is 0
So, y = 6 
So,
6=324a+12
-6=324a


Substitute the value in 1 
So,
Hence a function to represent the height of the ball in terms of its distance from the player's hands is 