Answer:
The rock remains in the air for t = 3.832 s
Step-by-step explanation:
To easily solve this equation, we can graph the equation with a calculator and see the interval for which the rock remains in the air.
(There is a minor problem with the equation, the last term should be 120 to model the 120 ft building)
h(t)= -16t^2 -30t + 120
Please see attached picture for the graph.
The time it takes for the ball to hit ground can be found by making
h(t) = -16t^2 -30t + 120 = 0
In the graph this point is equal to
t = 3.832 s
h(t) = 0
