The height of a flare fired from the deck of a ship in distress can be modeled by #h= - 16t^2+ 104t+ 56#, where #h# is the height in feet of the flare above water and #t# is the time in seconds. What is the time it takes the flare to hit the water?

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Answer 1 · 2017-01-11T04:50:17

t = 7 seconds

The flare hit the water when #h=0#

#-16t^2+104t+56 =0#

divide the equation by 8,
#-2t^2+13t+7=0#
#(-2t-1)(t-7)=0#

#-2t-1=0, t=-1/2#

#t-7=0, t=7#

since unit of time cannot be a -ve value, therefore t, time the flare hit the water is at 7s