Why is this coming back blank?

Im just trying to find the critical points. Why is it coming back blank?

Answer 1

[Walter Roberson]

You do not ask to display the results. We can see from the size information on the bottom left that exactly one result was found.

[Marina Pirzada]

How do I ask to display the results?

[Walter Roberson]

disp(CriticalPoints)

Answer 2

[Image Analyst]

What is blank? Your variable is empty, or nothing got printed out to the command window. You can take the semicolons off if you want to have results go to the command window. Also, as far as I know, diff() wants an actual number for the second argument, like 1 or 2, not some undefined symbolic x, unless there's a different diff for those of you who have the Symbolic Toolbox.

[Walter Roberson]

diff(expression, symbolic) is differentiation