1. Do Now: Add or subtract, if possible. 1.) 2.)

2. Academy Algebra II/Trig 12.4: Matrix Algebra HW: p.889 (8, 9, 12, 13, 16, 17, 21)

3. Scalar Multiplication. Given, ; find the following: 1.) 3A2.) -B

4. # columns of the first must be the same as the # rows of the second matrix. (r x c)(r x c) Multiplying Matrices

5. Determine if the matrices can be multiplied. 1.) 2.)

6. Operations Using Matrices Find the product AB if

7. Operations Using Matrices Find AB if

8. Operations Using Matrices Do Now: Find the product AB if

9. Academy Algebra II/Trig 12.4: Matrix Algebra HW: p.889 (19, 20, 26 – on calc, 27 – on calc)

10. Identity Matrix An identity matrix has the same number of rows and columns with the 1’s on the main diagonal and zeros for all other cells.

11. Operations Using Matrices Suppose that Find by hand and check your answers using your calculator. 1.) 2.)

12. Input Matrices on TI-89 Calculator: 1. Press APPS and select Data/Matrix 2. Select 3: New 3. Type– 2: Matrix, Folder– Main, Variable– a 4. Press ENTER, ENTER 5. Input Matrix A. 6. Repeat the steps above for matrix B. 7. Press HOME. 8. On the home screen you can add/subtract/multiply matrices. ** If you want to rewrite over a current matrix you can resize it by selecting F6 once you have opened the matrix. **

13. Input Matrices on TI-83/84 Calculator: 1. Press 2 nd X -1 to select MATRX 2. Arrow over to EDIT 3. Select a matrix to edit 4. Input the dimensions and # of the Matrix. 5. Repeat the steps above for matrix B. 6. Press 2 nd MODE to select QUIT and go back to home screen. 7. On the home screen you can add/subtract/multiply matrices: go to matrix menu and select matrices from the names menu.