Question 1032796: Billy-Bob Hicks missed the UGA game this past week, so he recorded the game using his
handy-dandy DVR. He made sure to stay off Facebook and Twitter because he knew his
friends would be talking about the game. After the game, Billy-Bob recieves a phone call
from Darealist Williams informing him of the outcome of the game. Natually, Billy-Bob is
upset that Darealist thought it necessary to tell him the score and, in his rage, hurls his cell
phone vertically upward from the top of a 96-foot building. The quadratic function
s(t) = -16t2 + 96t + 96 models the phoneʹs height above the ground, s(t), in feet, t seconds
after it was thrown. How many seconds does it take for the phone to hit the ground?
Round to the nearest tenth of a second if necessary.
Answer by fractalier(6550)   (Show Source):
You can put this solution on YOUR website! Well, given the equation
s(t) = -16t^2 + 96t + 96
we can find the height at any time t...we can also find t for any height s(t)...thus if we want to know when it hits the ground, s(t) = 0...so we have
0 = -16t^2 + 96t + 96
0 = -t^2 + 6t + 6
t^2 - 6t - 6 = 0
so that, using the quadratic formula we find,
and
t = 6.9 seconds (to the nearest tenth)
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