Substitute t=3 into the equation of motion.

The position of the last particle in 3X3 = 1+4*3-3*3=4m.

2)

When t=0, x = XO =1m.

The displacement of the first 3s is S=X3-Xo=4- 1=3m.

3)

Derive t to get V=4-2t. When t=2s, v = 0, and the object moves reversely between 2s and 3s.

X0= 1m，X2= 1+4*2-2*2=5m，X3= 1+4*3-3*3=4m

The displacement within 0-2S is S 1=X2-X 1=4m.

S2=X2-X3= 1m internal displacement

Total distance S=S 1+S2=5m.

4)

Position-the coordinate point where the particle is located or passes.

Displacement-vector, indicating the change (movement) of position, pointing from the initial position to the final position.

Distance-scalar, the size of the motion path. In one-way linear motion, distance = displacement.