The path of flight (trajectory) of a football thrown by a quarterback is described by the following function: where y = vertical position of football relative to the ground (m) x = horizontal position of football relative to launch position (m)
How high above the ground is the football when it is 30 meters downfield from the quarterback?
A)1.1 m
B)2.2 m
C)28 m
D)7.9 m

Question

The path of flight (trajectory) of a football thrown by a quarterback is described by the following function:  where y = vertical position of football relative to the ground (m) x = horizontal position of football relative to launch position (m)
How high above the ground is the football when it is 30 meters downfield from the quarterback?
A)1.1 m 
B)2.2 m 
C)28 m 
D)7.9 m

Quizplus · Accepted Answer

We substitute x = 30 into the function and solve for y:
y = -0.001x^2 + 0.09x + 1
y = -0.001(30)^2 + 0.09(30) + 1
y = -0.9 + 2.7 + 1
y = 2.8
Therefore, the football is 2.8 meters above the ground when it is 30 meters downfield from the quarterback. The closest choice is D: 7.9 m, which is not the correct answer.

The Path of Flight (Trajectory) of a Football Thrown by a Quarterback