math
posted by Anonymous .
an object is thrown upward from the top of a 80foot 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)(t5) = 0
t = 5 or 1 , we will reject the last answer
the object will hit the ground after 5 seconds