Answer:
a) The vertex of the graph is 
 , b)
, b) 
 , c) The equation of the parabola is
, c) The equation of the parabola is 
 .
.
Explanation:
a) The tennis ball experiments a free fall, that is, an uniform accelerated motion due to gravity and in which effects from Earth's rotation and air viscocity are negligible. The height of the ball in time is represented by a second order polynomial. Hence, the vertex of the parabola is the initial point highlighted in graph. 
The vertex of the graph is 
 .
.
b) If we know that 
 ,
, 
 and
 and 
 , then the value of
, then the value of 
 is:
 is:
 
 




c) The equation of the parabola is 
 .
.