Hello, all. I am reading Serge Lang's "A First Course in Calculus" in order to get a better understanding of the topic. I thought I would read his review of fundamental concepts, and, naturally, it has been a breeze so far. However, I am stumped when trying to work out this problem: I do not see how [tex] 2ab \leq 2|a||b| [/tex] turns into [tex] (a+b)^2 = a^2 +2ab + b^2 [/tex] Any help in resolving this is greatly appreciated. I don't want to move on without understanding this bit. It's really bothering me. Also, I apologize for not adhering to the established template. I didn't see a way to formulate this question in a way that fit the template.