Question

A football is kicked into the air from an initial height of 4 feet. The height, in feet, of the football above the ground is given by s (t)=-16^2+50t+4, where t is time, in seconds, and t>=0. At what time will the football be 25 feet above the ground?

3.625 seconds
3.20 seconds
0.5 seconds or 3.625 seconds
0.5 seconds or 2.625 seconds

Answer 1

Answer: D(0.5 seconds or 2.625 seconds)

Hope this helps :)

Answer 2

To answer the question above, substitute the given value of height.
25 = -16x² + 50t + 4
Solving the following equation by the use of quadratic formula,
x = (-b +/- sqrt (b² - 4ac)) / 2a
Subsituting the known values of a, b, and c
x = (-50 +/- sqrt (50² - 4(-16)(-21)) / 2x-16
The values of x are 0.5 and 2.625. Therefore, the answer is the fourth choice.