Question 320741
A diver's height h above the water t seconds after diving is given by
 h = -16t^2 + 64. How long does a dive last? 
:
Replace h with sea level, which is 0, solve for t
-16t^2 + 64 = 0
-16t^2 = -64
divide both sides by -16, this also changes the signs
t^2 = 4
t = {{{sqrt(4)}}}
t = 2 seconds