We are expected to be familiar with this formula: .A rocket loaded with fireworks is to be shot vertically upward from the ground level
with an initial velocity of 200 feet per second.
When the rocket reaches a height of 400 feet on its upward trip, the fireworks will be detonated.
How many seconds after liftoff will this take place?
. . where is the height of the rocket (in feet) seconds after liftoff.
When is ?
We have: .
. . which factors: .
. . and has roots: .
The fireworks will be detonated seconds after liftoff.