Determining the Transfer Function of a Wheatstone Bridge
Tansfer functions are written Vout/Vin, so in your case
V-/Vin = pot/(pot+R1)
V+/Vin = R1/(R1+R1) = 1/2

Usually the outputs of a Wheatstone Bridge are put into an instrumentation or differential amplifier. Then the transfer function will change to something like the following:

tf_inst_amp = (V+/Vin - V-/Vin) * gain_of_diff_amp = (V+-V-)*gain_of_diff_amp/Vin