An explosives company specializes in bringing down old buildings. The time it takes for a particular piece of flying debris to fall to the ground can be modelled by the function h(t)= -12(t+2)^2 + 120(t+2), where h is the height of the debris in metres and t is the time in seconds.

Question

An explosives company specializes in bringing down old buildings. The time it takes for a particular piece of flying debris to fall to the ground can be modelled by the function h(t)= -12(t+2)^2 + 120(t+2), where h is the height of the debris in metres and t is the time in seconds. 
1.) How long will it take for the piece of debris to hit the ground after an explosion? Show all work

Steve · Answer

it hits the ground when h=0. So, just solve -12(t+2)^2 + 120(t+2) = 0 or, if you prefer t^2-6t-16 = 0