Question 200633
If an object is projected upward with an initial velocity of 48 ft per second
 from a height h of 160 ft, then its height t second after it is projected is
 defined by the equation h= -16t 2 + 48t + 160.
:
 How many seconds after it is projected will it hit the ground?
;
When the object strikes the ground h = 0, therefore:
-16t^2 + 48t + 160 = 0
:
Simplify, divide by -16 
t^2 - 3t - 10 = 0
Factor
(t - 5)(t + 2) = 0
Positive solution
t = 5 seconds to hit the ground
:
:
Check solution in original equation
h = -16t^2 + 48t + 160
h = -16(5^2) + 48(5) + 160
h = -400 + 240 + 160
h = 0