So let me do that same green. So right after that, the function starts increasing again. f prime of x is greater than zero. So this seems like pretty good criteria for a minimum point. f prime of x switches signs from negative to positive as we cross a. If we have some critical point a, the function takes on a minimum value at a if the derivative of our function switches signs from negative to positive as we cross a, from negative to positive. Now once again, this point right over here, this critical point, x sub 3, does not meet that criteria.