Question

two charges + q and minus q are separated by a distance of 9 metre then the distance from + q at which the electric potential is zero

Answer 1

as both charge are equal in magnitude but opposite in charge so the elecric potential lie at mid point.

so the distance is 4.5m.

or

you can calculate it also

take x be the distance from +q at which electric potentia is zero ...

so for -q the distance is 9-x.

with the help of it you can also find distnce