After a punter kicks a football, its height s, in feet above the ground, is given by s = −16t 2 + 15t + 1, where t is in seconds.
How long will the football be in the air?

Question

After a punter kicks a football, its height s, in feet above the ground, is given by s = −16t 2 + 15t + 1, where t is in seconds.
How long will the football be in the air?

mathmale · Answer

When the ball hits the ground, its elevation will be y = ?
Use this information to solve the given equation for t.  You'll get two results; one will be the answer you're looking for, while the other will be extraneous (negative) and thus not useful.