Answer
After it reaches X=6m, the particle is traveling in the negative direction.
Work Step by Step
For the first 3 meters, the particle is pushed in the positive direction. For the next 3 seconds, the particle is pushed in the negative direction with an equal magnitude. At X=6m the particle's motion is stopped. The particle is still being pushed in the negative direction for the next second, causing the particle to change directions and travel in the negative direction.
