6. The trajectory of an object that is thrown
from the top of a building with an initial
velocity of 50 meters per second is modeled
as h=-4.91 + 501 + x, where h is the height
in meters of the object at a given time, t is
the time in seconds, and x is the height of the
building in meters. If the object hits the
ground after 21 seconds, what is the
approximate height, in meters, of the
building?