I'm trying to find the voltage betwen point A and B(the point that must be 0 to be the bridge balanced) I know i must use the voltage divider formula to find voltage from point A to ground ie. 3V, then i calculate the point B to ground voltage and is ie. 2v, to find the voltage betwen this 2 points i must substract 3v-2v = 1v.

why i substract v1 from v2 and not v1+v2, or v1/v2? whats the theory why this 2 voltages must be substractedand not added or divided?

thanks for any help

and please excuse my poor english