Step-by-step explanation:

Answer:
, 
Step-by-step explanation:
The velocity function of the projectile is obtained by deriving the position function:

Now, the velocities after 3 and 15 seconds are, respectively:




Answer: -4
Step-by-step explanation:
3x + 4 = -8
3x= -12
x = -4
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Answer:
Decay
Step-by-step explanation:
The equation shown has a ratio(number raised to the power) less than 1, so therefore it is decay. This basically comes from the fact that if you raise a number less than 1 to a power, it become smaller than the number itself.
(In the cases talked about above, we are neglecting negative numbers)