Two point sized identiacal sphere carrying charge `q_(1)` and `q_(2)` on them are separated by acertain distance the mutal force between them is `F` these two are brought in contant and kept at the same separation Now the force between them is `F^(1)` then .`(F^(1))/(F)=((q_(1)+q_(2))^(2))/(4q_(1)q_(2))`

Explanation

when charges separated by certain distance the force is given by
Then `F=(1)/(4piepsilon_(0))(q_(1)q_(2))/(r^(2))……..(1)`
when charges brought in contant and kept at the same distance the force is given by
`F^(1)=(1)/(4piepsilon_(0))(q_(1)+q_(2))^(2)/(4r^(2))……..(2)`
" From " (1) and (2), `:.(F^(1))/(F)=((q_(1)+q_(2))^(2))/(4q_(1)q_(2))`