Math 104 Assignment 2 common mistakes

• In 1.C. there were many circular arguments: people assuming that taking square roots preserves order while trying to prove that taking square roots preserves order.
• In 2.A., many people were still assuming that $\sup(E) \in E$ or equivalently that $E$ has a maximum element.
• In 3., there were some attempts of "proof by example", which is not a valid proof technique.