Not entirely sure on how to incorporate the third resistor on the positive terminal into the transfer function? Any ideas

 

The third resistor is not part of the transfer function. It is a DC current path and voltage reference necessary for the op-amp to function at all. R3 does not affect the gain at any frequency.

Peek inside the op-amp and see how this works. (Pretend I drew a push-pull output on the op-amp.)

 

The third resistor is not part of the transfer function. It is a DC current path and voltage reference necessary for the op-amp to function at all. R3 does not affect the gain at any frequency.

Peek inside the op-amp and see how this works. (Pretend I drew a push-pull output on the op-amp.)

I also thought the same. Just wanted to verify with someone else. Cheers!