Question

If an object is propelled upward from a height of 16 ft at an initial velocity of 80 feet per sec, the its height after t seconds is given by the equation h=-16t²+80t+16, where h is in feet. after how many seconds will the object reach a height of 116 ft?

Answer 1

116 = -16 t^2 + 80 t + 16

16 t^2 - 80 t + 100 = 0

4 t^2 - 20 t + 25 = 0

(2 t- 5)^2 = 0

t = 5/2 = 2.5 seconds