Answer:

Explanation:
Position of charge q₁ is (0,0)
Position of charge q₂ is (x₁,0)
So, the electric potential energy between the charges is given by :

Now the position of charge q₂ has been changes from (x₁,0) to (x₂,y₂). Now, electric potential energy between the charges is :

We know form the work energy theorem that, the change in potential energy is equal to the work done. Mathematically, it is given by :





Hence, the work done by the electrostatic force on the moving point charge is
. Hence, this is the required solution.