The function f of x is equal to negative 10 x open paren x minus 4 close paren 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?

The projectile is on the ground when its height is 0, so set −10x(x − 4) = 0. The solutions are x = 0 and x = 4: launch occurs at 0 seconds, and landing occurs at 4 seconds. Therefore, the projectile stays in the air for 4 seconds.

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