Two point charges +q and -q are separated by a distance d. Except at infinity, where can the electric potential due to these two point charges be zero?

Explanation

The electric field is zero at point p, only, if field due to charges +Q balances the field due to charge +4Q.
`:.(1)/(4piepsilon_(0))*(Q)/(x^(2))=(1)/(4piepsilon_(0))*(4Q)/((6a-x^(2)))rArr(1)/(x^(2))=(4)/((6a-x)^(2))`

`rArr(1)/(x)=(2)/((6a-x))`
`rArr2x=6a-xrArrx=2a`
`:.` The required point is at a distance of 2a from +Q.