7. Consider a function f(x). Assume that f'(x) and f"(x) are always defined. (a) If (x, y) is an inflection point of f, is it necessarily true that f"(x) = 0, or might it be possible that f"(x) # 0? (b) If f"(x) = 0, is it necessarily true that (x, f(x)) is an inflection point of f, or might it be possible that (x, f (x)) is not an inflection point of f