Electronic Circuits – Nodal Equation assistance required.

Hi All,
I have a come to a stop here, any assistance in breaking this exercise down for me would be greatly appreciated.

Please see the figure - I have been asked to write the nodal equations for the "bridge configuration" of this figure, by way of the "format approach"

Can somebody please enlighten me?

Thank you for your consideration.

We don't mind helping you but we won't do all of the work for you. Please post what you've already done including any ideas you've had and we might be able to make some suggestions. If you've got completely no idea then may be it's your lecuturer's fault and it isn't right that you make him/her look good by cheating and copying from the Internet.

some clues

this cct is solved by using only 2 nodes and the node at the bottom will be considered groun try it and let me know if u have any difficulty
by the way 2 nodes are one at the top of the bridge and other is connnected to 1k resistor in the middle and connected to -ive termeinal of 9V