Derive an expression for potential at a point due to a group of point charges?

Define electric potential at a point. Derive an expression for the potential at a point due to a point charge.

Derive an expression for electric potential at a point due to a point charge.

Deduce an expression for potential at a point due to gravitational field.

Derive an expression for electric potential at-a point due to an electric dipole with the help of diagram and hence calculate electric potential when the point is on the axial lline of electric dipole.