This one I forgot to include with my previous question.

A particle moves along a line so that its position at any time t≥0 is given by the function s(t)=tł-8t+1, wheresis measured in feet andtis measured in seconds.

Find the average velocity during the first 3 seconds, and at what values oftdoes the particle change direction?

My answer for the average velocity is 5ft/s, and my answer for the second part is 1.60s and -1.60s.

How close am I?