A rocket is fired from a plane flying horizontally at 9000 ft. The height h (in ft) of the rocket above the plane is given by h = 560t − 16t², where t is the time (in s) of flight of the rocket. When is the rocket more than 4000 ft above or below the plane? See Fig. 17.36.

Fig. 17.36.

T 4000 ft 4000 ft 9000 ft h