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

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25 January, 13:06

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Jose Mckee · 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.