Answer:
It takes 3 seconds over the interval [0,3]
Step-by-step explanation:
To find when the roller coaster reaches the ground, find when d=0.
To solve divide each term by 16 and factor:
Solve for t by setting each factor to 0.
t-3=0 so t=3
t+3=0 so t=-3
This means the car is in the air from 0 to 3 second.
