1. 4.2 Matrix Multiplication Objectives: Multiply 2 matrices. Use matrix multiplication to solve mathematical and real-world problems. Standard: 2.8.11.1 Use matrices to organize and manipulate data, including matrix multiplication.

2. MATRIX MULTIPLICATION INVOLVES MULTIPLICATION AND ADDITION.

4. EX. 1

5. *Let * Find AB, if it exists. * Find BA, if it exists. and

6. * Let and * Find AB, if it exists. * Find BA, if it exists.

7. * Let and * Find AB, if it exists.

8. MATRIX MULTIPLICATION IS NOT COMMUTATIVE!!

12. PSSA WARM-UP QUESTION Algebra II - Chp. 4 Standard 2.8.11 D Model Situations.  How is the size of a matrix determined? How can the location of an individual entry be identified? How can matrices be used to model situations?

13. Writing Activities: 3). Which pair (s) of the matrices above can be added? Explain. 4). Which pair(s) of the matrices above can be multiplied? Explain.

14. Writing Activities 5). For the given matrices, does AC equal CA? Explain. 6). What must be true of matrix M in order for you to be able to find M 2 ? 7). What are some of the differences between addition and multiplication of matrices and addition and multiplication of real numbers?