Op Amp Summing Point Problem (Ideal)
For this circuit, look at the second opamp first.


What is the relationship between \$V_{O1}\$ and \$V_{O2}\$?
What does this imply about the Thevenin equivalent of the opamp and the two 4R resistors, considered as a source driving the input of the first opamp, as a function of \$V_{O1}\$?