I have been teaching myself analysis with baby rudin. I have just started chapter three in the past week or so and one thing I am having trouble with is the proofs which use the binomial theorem and various identities derived from it. Rudin pretty much assumes this material as prerequisite and his proofs use it so concisely that it is hard for me to follow since I pretty much learned the binomial theorem while studying rudin. A good example of where I have trouble is 3.20. This theorem uses a few different identities derived from the binomial theorem which I am not familiar with and and it is hard for me to just learn in the context of these proofs. A good example of where I have no trouble is theorem 3.31. This theorem requires just a straightforward use of the binomial theorem itself which I am fine with. Is there a good textbook or website to get me up to date on these identities involving the binomial theorem?