Does an integral domain has to have a unity? If not, what is an example of integral domain having no unity? If so, what is a proof for this?
I just took an algebra course on group and rings last term and didn't do too well (got a C) because I could not produce proofs fast enough on my exam. What should I do and what resources can I use to improve if I want to study further pure maths subjects? Should I just give up?