Question

An object is propelled vertically upward from the top of a 224-foot building. The quadratic function s(t)=-16t^2+128t+225 models the balls height above ground, s(t), in feet, t seconds after it was thrown. How many seconds does it take till the object finnaly hits the ground? Round to the nearest tenth of a second if necessary

Answer 1

set s(t)=0, its roots are the time the ball had height 0.
use quadratic formula, clearly it was in the air for 0 to t for some positve t value.