need help on this math problem

Question

An object is thrown upward from the top of a 64-foot building with an initial velocity of 48 feet per second. The height h of the object after t seconds is given by the quadratic equation h equals negative 16 t squared plus 48 t plus 64. When will the object hit the ground?

Answer 1

h(t) = -16t² + 48t + 64

 

Set h(t) = 0 and solve the resulting quadratic equation for t.

 

-16t² + 48t + 64 = 0 ⇒

 

t² - 3t - 4 = 0

 

(t + 1)(t - 4) = 0

 

t = -1 or 4

 

Since time starts at t = 0, the answer is 4 seconds.  Test the answer.