Mr. Altarac's method of completing the square

1) Her is what I do when the unknown is the parameter in front of the x squared term:
http://www.youtube.com/watch?v=mKj7LPbF7Bo

2) Here is what I do when the unknown is the parameter in front of the x term:
http://www.youtube.com/watch?v=D_xz7qPFglM


3) Here is what I do when the unknown is the last parameter:
http://www.youtube.com/watch?v=RwDgQN_9wOM