I have the following circuit.... I have managed to derive an equation for U2: Now I want to substitute U2 into U1, in order to derive equation for U1 I have defined U1 as: Now I substitute U2 into the above equation. This is how far I get.....I am stuck... My circuit simulator is saying that U1 is equal to: However I cannot simplify to get this equation. Can someone please help I have spent hours trying to get U1 to look like the U1 that the simulator produces. I thank you in advance.