charges q and 9q separated by distance r how much distance the electric field will be zero

Let a test charge q• be placed at a distance x from charge q at point P.So, now by equating the magnitude of Electric field on test charge we get the equation:(2x-r)(8x+r)=0That means at a distance r/2 b/ both charges their will be EF zero And r/8 distance away from charge q EF wil be zero.I hope this helps.Thanku