analog circuit nodal analysis
An RC twin T circuit like this will generally have the transfer function: -



For the circuit below: -



Even with R1 = R2 etc it's by no means a simple thing you are asking so I would say to you this... 


  Here's the answer (above) and it can be simplified to give the desired
  answer in your question, but where are you getting stuck i.e. how far
  have you got with solving this?