Answer
Function 2 is directed opposite the rock's initial direction.
Work Step by Step
If you plug in a positive number for t on all the functions, you will get a positive value for X in functions 1 and 3, and a negative value for X in function 2. The rock is initially traveling in the positive direction, therefore function 2 is the only function that is directed opposite to the rock's initial direction.
Example: let t=10
1)x=4(10)-3_________________x=37
2)x=-4($10^{2}$)+6(10)-3______x=-343
3)x=-4($10^{2}$)+6(10)-3______x=457
