Solution:

Electric potential is the amount of work done to move a unit positive charge from infinity to that point against the electric field.

1. Calculation of potential due to q1 at various points

The electric potential due to point charge q1 at a distance r from it is given by V1 = kq1/r, where k is the Coulomb constant.

At x = 0, r = 0, and V1 = infinity.

At x = 6, r = 6, and V1 = kq1/6.

2. Calculation of potential due to q2 at various points

The electric potential due to point charge q2 at a distance r from it is given by V2 = -kq2/r.

At x = 0, r = 6, and V2 = -kq2/6.

At x = 6, r = 0, and V2 = -infinity.

3. Calculation of net potential at various points

The net electric potential at any point is the algebraic sum of the potentials due to all the charges present.

At any point between x=0 and x=6, the net potential will be zero if V1 = -V2.

Therefore, kq1/6 = kq2/6, or q1 = -q2.

Hence, if a point charge of magnitude 2 is placed at x=0 and a point charge of magnitude -1 is placed at x=6, then the net electric potential will be zero at the point x=2, where the distance from q1 is 2 and the distance from q2 is 4.

Conclusion:

Thus, the electric potential is zero at the point x=2.