Assuming the voltage of the negative terminal is 0, how calculate the voltage of point A and B? And can anyone draw a simpler equivalent circuit for me. God bless the people helping me.

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beside, why am I not allowed to use the image extension on this board?

 

You may want to post your image in a manner in which it is easier to access if you would like for someone to help you out. It is currently requiring me to log into google to view the image.

 

This should help you: http://en.wikipedia.org/wiki/Wheatstone_bridge