2/5,1/2,6/10 hope that helped!
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:
The equation is an differential equation of second order.
The dependent variable is x, while t is the independent variable.
Step-by-step explanation:
The order of the equation depends on the greatest grade of the derivative, in this case it's the second derivative (x'')
Since x is a function of t, we would have that t is the independent variable while x is the dependent variable.