The path of a punted football is given by the function:f(x) = (-16/1225)x^2 + (7/5)x + 2.5
where f(x) is the height (in feet) and x is the horizontal distance (in feet) from the point at which the ball is punted.
How long is the punt?

Question

The path of a punted football is given by the function:f(x) = (-16/1225)x^2 + (7/5)x + 2.5
where f(x) is the height (in feet) and x is the horizontal distance (in feet) from the point at which the ball is punted.
How long is the punt?

aum · Answer

When the ball hits the ground, the height f(x) will be zero. 
Set f(x) = 0 and solve for x. Since this is a quadratic you will get two values. 
Throw away the negative x value and keep the positive x value. 
That will be the length of the punt in feet.