3. We have learned the definitions of concavity (up and down) for differentiable functions following Definition 4.6.1 in the textbook. In this question, we learn a new definition of concave-up (also known as convex) that applies to any function as long as the function is defined on an interval, not necessarily differentiable. An important question, then, would be " are these two definitions equivalent to each other for differentiable functions?" You are going to show that it is partially true. Let f be a function defined on an interval (a, b). We say that a function f is convex if for every a