DR. Strang thank you for a powerful lecture on the Survey of Difficulties with Ax=b. In linear systems this equation is displayed in many technical books, with little or no thought about it's difficulties. From watching this lecture, the difficulties of this equation is explained in great detail.####[['DR. Strang', 'Instructor', 'POS'], ['lecture', 'Course_General_Feedback', 'POS'], ['Survey of Difficulties', 'Mathematical_Related_Concept', 'POS'], ['Ax=b', 'Mathematical_Related_Concept', 'POS'], ['linear systems', 'Mathematical_Related_Concept', 'POS']]