About Lesson
Elementary Linear Algebra: Applications Version, 11th Edition (http://bcs.wiley.com/he-bcs/Books?action=index&itemId=1118434412&bcsId=8466)
Determinant after row operations(https://www.khanacademy.org/math/linear-algebra/matrix-transformations/determinant-depth/v/linear-algebra-determinant-after-row-operations)
Upper triangular determinant(https://www.khanacademy.org/math/linear-algebra/matrix-transformations/determinant-depth/v/linear-algebra-upper-triangular-determinant)