math help. Word problem Algebra?
A ball is thrown from a height of 80 feet with an initial downward velocity of 4ft/s . The ball's height h (in feet) after t seconds is given by the following.
h=80-4t-16t^(2)
How long after the ball is thrown does it hit the ground?
Round your answers to the nearest hundredth.
Please answer and explain. Thanks for the help!
Comments
Well, let h = 0 and solve for t!
0 = 80 - 4t - 16t²
0 = 4(20 - t - 4t²)
Use quad. formula...
t = (-b ± √(b² - 4ac))/2a
= -(1 ± √((-1)² - 4(-4)(20)))/8
= 1/8 * (√(321) - 1) [which is the answer]
Good luck!