A launched rocket has an? altitude, in? meters, given by the polynomial hplus +vtminus -4.9tsquared 2?, where h is the? height, in? meters, from which the launch? occurs, at velocity v in meters per? second, and t is the number of seconds for which the rocket is airborne. If a rocket is launched from the top of a tower 70 70 meters high with an initial upward speed of 20 20 meters per? second, what will its height be after 3 3 ?seconds?