
Mark H. answered 01/14/20
Tutoring in Math and Science at all levels
Let's assume that + means moving to the right.
We need the velocity, so take the 1st derivative:
v = s' = -t2 + 13t - 30
For small t, the 3rd term dominates (moving left)
Find where v goes to zero:
-t2 + 13t - 30 = 0
t = 3 and t = 10
So v is positive for 3 < t < 10 (But we only evaluate up to t = 9