1. Matrices

2. What you need to learn Know how to write a Matrix Know what is ORDER of Matrices Addition and Subtraction of Matrices Multiplication of Matrices Using Matrices to solve simultaneous equations (Find determinant, Inverse) Using Matrices to solve word problems

3. Resources Textbook Ch 1 (Section 1.3) – for Solving simultaneous equations Notes in this powerpoint Other notes and worksheets attached

4. Matrices – How to write & What is Order AppleOrangePear Shop 110.50.3 Shop 2210.5 2 rows and 3 columns  Matrix has order 2x3 (read as “2 by 3”)

5. Matrices E.g: A drink stalls sold 160 cups of coffee, 125 cups of tea and 210 glasses of soft drinks on Monday. On Tuesday, it sold 145 cups of coffee, 130 cups of tea and 275 glasses of soft drinks. On Wednesday, it sold 120 cups of tea, 155 cups of coffee and 325 glasses of soft drinks. Design a matrix to represent this information. State the order of your matrix. C T SDM T W order 3x3 OR

6. Matrices Matrix Operations B – A ? Observation 1: Matrices must be same order to add or subtract

7. Matrices Observation 1: A + B = B + A  Addition is commutative Observation 2: (A + B) + C = A + (B + C)  Addition is associative

8. (3 × 3) + (4 × 1) = 13(3 × 2) + (4 × 1) = 10 (1 × 2) + (3 × 1) = 5 (1 × 2) + (2 × 1) = 4 Matrices Scalar Multiplication: Matrix Multiplication: Remember: ROW multiply by COLUMN Play as slide show

9. Matrices An electrical shop sold 5 televisions, 10 VCD players and 15 DVD players on Monday. On Tuesday, it sold 7 televisions, 8 VCD players and 9 DVD players. Given that the price of television is $90, the price of VCD player is $40 and the price of DVD player is $80, find the total sales for Monday and Tuesday. MTMT TV VCD DVD Total for Monday Total for Tuesday $T $V $D

10. Matrices

11. B A  Not possible! (2 x 2) (3 x 2) Not equal!  Can only multiply matrices if these numbers are the same!

12. Matrices Observation 1: Observation 2: (AB)C = A(BC)  Multiplication is associative AB = BA  Multiplication is NOT commutative!

13. Matrices The matrix with all entries zero is called a null matrix. This matrix is called the identity matrix. The diagonal are all 1’s. Observation 1: A0 = 0A = 0 Observation 2: AI = IA = A

14. *Inverse Matrices* The inverse of the matrix A = is given by,  Determinant of A

15. *Inverse Matrices*

16. Practice Find (a) BA (b) BA – 2A If, find a and b.

17. Answer a = − 8, b = 238