Question 389336
The man jumped off the cliff at 480 feet (The height of the cliff, when t = 0.)
The highest point reached is {{{(4ac - b^2)/(4a) = (4*-16*480 - 256)/(-64) = 484}}} feet. (Or 4 feet above cliff level.)
To find the length of time it took him to hit the water, solve for t in
{{{0 = -16t^2 + 16t + 480}}}; 
{{{0 = t^2 - t - 30}}};
(t-6)(t+5) = 0
The man will hit the water after 6 seconds.  (Eliminate the negative value of t.)