1. The problem statement, all variables and given/known data In an over hand serve, the ball starts from a point 2m above the ground and travels a horizontal distance of 20m before it strikes the floor. The ball travels in a parbolic path and reaches its highest point after travelling a horizontal distance of 9m as show in the link below: http://img407.imageshack.us/my.php?image=asdaq2.jpg Determine the equation of the parabola in the form y-k=a(x-9)^2 2. Relevant equations y-k=a(x-h)^2 3. The attempt at a solution Well i know that the ball reaches its maximum height 9 feet from where it was served. If we let x=0 be where the ball was served, then we know the x coordinate of the vertex is 9, so the equation is of the form y-k=a(x-9)^2 To finish the equation precisely, I need to determine the values of a and k. To do that, I need two equations relating the values of a and k. But the given information provides with what I need to write those two equations --I know the x and y values (1) where the ball was served and (2) where it hit the ground. but i'm still confused ! i could use some help:) could somebody solve it for mee pleaaase??