Reviewing for my final, I came across a question on an old final that is rather unfamiliar. The question has a graph of a function f(x), and it asks you to find the limits at certain values. The last two questions are f'(2) and f"(3). Strangely, we have never learned in class how to find the derivative by looking at the graph of a function, and my textbook barely touches upon it. I know what the definition of a derivative is, but when viewing it this way I am finding it difficult.

How do I go about this? It is probably the most basic part of derivatives, but we never learned it! Thanks!