posted by Anonymous .
an object is thrown upward from the top of a 80-foot building with a initial velocity of 65 feet per second. The height h of the object after t seconds is given by the equation h=-16t2+64t+80. when will the object hit the ground
Your equation does not match your data
if the equation is
h = -16t^2 + 64t + 80 , then the initial velocity was 64 ft/sec, not 65 like you typed.
I will go with the 64
-16t^2 + 64t + 80 = 0
divide each term by -16
t^2 - 4t - 5 = 0
(t+1)(t-5) = 0
t = 5 or -1 , we will reject the last answer
the object will hit the ground after 5 seconds