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?

For 4 seconds the projectile will be in the air.

Step-by-step explanation:

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.

Now, if the projectile stays for x seconds in the air then after x seconds its height will be zero.

Hence, 0 = - 10x (x - 4)

⇒ x = 0 or x = 4

Now, x cannot be 0 as at time = 0 the projectile starts its motion.

So, for 4 seconds the projectile will be in the air. (Answer)