I am completely confused as to what to do on this someone please help!
A particle moves along a straight line and its position at time t is given by
s(t)=(2t^3)-(21t^2)+72t t0 where s is measured in feet and t in seconds.
Use interval notation to indicate the time interval or union of time intervals when the particle is moving forward and backward.
And Use interval notation to indicate the time interval(s) when the particle is speeding up and slowing down.

Question

I am completely confused as to what to do on this someone please help!
A particle moves along a straight line and its position at time t is given by 
s(t)=(2t^3)-(21t^2)+72t t>0 where s is measured in feet and t in seconds. 
Use interval notation to indicate the time interval or union of time intervals when the particle is moving forward and backward.
And Use interval notation to indicate the time interval(s) when the particle is speeding up and slowing down.