What happens when you put x's and y's under the square root sign along with the numbers? It's not as bad as you think.
OOPS! To create playlists you must logged in.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)