Question

The function f(x) = –10(x)(x – 4) represents the approximate height of a projectile launched from the ground into the air as a function of time in seconds, x. How long, from launch to landing, does the projectile stay in the air?

0 seconds
1 second
2 seconds
4 seconds

Answer 1

Set f(x) = 0: -10x(x − 4) = 0 ⇒ x = 0 or x = 4.

The projectile is in the air from t = 0 to t = 4 seconds, so it stays in the air 4 seconds.