The firework reaches the ground after 6.25 seconds.
A projectile is the curved motion of an object thrown into space under the influence of gravity.
Given that the firework experiences a projectile motion given by the equation:
h = -16t² + 84t + 100
where h is the height after t seconds.
The firework reaches the ground when h = 0, hence:
0 = -16t² + 84t + 100
t = 6.25 seconds.
Therefore the firework reaches the ground after 6.25 seconds.
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