Answer: 20 feet
Explanation:
The vertex form of a quadratic equation is: y = a(x - h)² + k
where (h, k) is the vertex
h is the axis of symmetry (time at which maximum height is reached)
k is the maximum height
Given: y = -(x - 7)² + 20
--> h = 7, k = 20
therefore, the maximum height of the ball is 20