Matrix Multiplication

Fundamental Law of Matrix Multiplication AB times C equals A times BC

To multiply AB: If A has n columns, B must have n rows.

1. The entry in row i and column j of AB is (row i of A) · ( column j of B) .

2. Matrix A times every column of B

3. Every row of A times matrix BA

4. Multiply columns 1 ton of A times rows 1 ton of B. Add those matrices.