An object is thrown upward from the top of an 80ft tower. The height h of the object after t seconds is represented by the quadr
atic equation h=-16t^2+64t+80. After how many seconds will the object hit the ground?
a)29 seconds
b)6.4 seconds
c) 5.0 seconds
d) 8.0 seconds
1 answer:
0 = -16t²+64t+80
Finding the roots of the equation:
-16(t² - 4t - 5) = 0
-16(t-5)(t+1) = 0
t = 5, t = -1. Time cannot be negative, so after 5 seconds it will hit the ground.
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