Khan Academy: Linear Algebra: Unique Row Space Solution to Ax = B

A video lesson proving that there is a unique solution in the row space of A to the equation Ax = b, where A is some m x n matrix, b is a vector that is a particular member of the column space of A, and x is a member of Rn. The solution in the row space is the smallest solution to the equation Ax = b. [19:12]