Two point charges Q and −Q/4 placed along the x-axis are separated by a distance r. Take −Q/4 as origin and it is placed at the right of Q. Then the potential is zero.
Potential in the right of charge -Q/4= −kQ4x1+kQr+x1=0orr+x1=4x1orx1=r/3
Potential in the left of charge -Q/4 at distance x2 = −kQ4x2+kQr−x2=0orx2=r5