Well, as I’m here, I want to ask for reopen votes on this problem:math.stackexchange.com/q/3338982/624428 It was closed for missing context, but the OP had edited it so I think it should be reopen.
Haven’t read many books, since I just begin my third year as an undergraduate. I like Durrett’s probability: theorem and examples and Le Gall’s Brownian motion, martingales, and stochastic calculus. For analysis, I’m a big fan of E.M.Stein.
@FengShao The question has been edited, but I don't see how any new context has been added (the only significant edit I see, other than formatting, is correcting 1/2x to \frac{x}{2}.
@XanderHenderson In the fourth edition, the OP added “such that g(c)=0”. So it did have a whole context, and the OP mentioned what he had tried in the very first edition.
@FengShao That detail, I would argue, is not context, but actually correcting the statement of the question.
It took the question from "unclear" to "clear".
Context is about motivation, a source for the problem, the knowledge of the asker, etc.---anything which will help an answerer to write an answer which will align well with what the asker needs.
Some minimal context has been provided by the asker (we know that they know of the existence of the Mean Value Theorem and Rolle's Theorem), but they also provided a rather confusing comment about "plotting" this function.
By the way, I say this not to convince you---there is a spectrum from inclusionist to deletionist, and I occupy a position fairly far over on the deletionist end of things. However, knowing what some others mean by "context" may be useful.