4.4.2 Matrix-matrix multiplication: Definition

4.4.2 Matrix-matrix multiplication: Definition

[jackchan]

Hi, I am a little confused. 5:01

if matrix B is the collection of unit-basis vectors of the vector x, wouldn't that mean 'k' would equal to 'n' (i.e. the number of rows in the matrix must be the same as the number of rows in the vector)?

If so, when would there be a concrete case where k =/= n?

Thank you.