Answer:
t=11 sec
Step-by-step explanation:
The position of the particle moving along the x-axis is given by:
[tex]s(t) = {t}^{3} - 18 {t}^{2} + 33t + 14[/tex]
The velocity is given by:
[tex]s'(t) = 3 {t}^{2} - 36{t} + 33[/tex]
If s'(t)>0 then the particle is moving right.
[tex]3 {t}^{2} - 36{t} + 33 \: > \: 0 \\ {t}^{2} - 12{t} + 11\: > \: 0[/tex]
[tex] \implies \: t \: < \: 1 \: or \: t \: > \: 11[/tex]
This means that the particle is moving left when
[tex]1 \: < \: t \: < \: 11[/tex]
The particle changes direction at time t=1 or t=11