Do Now: Add or subtract, if possible.

85

21

602

513

121

740

318

014

1.)

2.)

Academy Algebra II/Trig12.4: Matrix AlgebraHW: p.889 (8, 9, 12, 13, 16, 17, 21)

Scalar Multiplication.

Given , ; find the

following:

85

21A

121

740B

1.) 3A 2.) -B

# columns of the first must be the same as the # rows of the second matrix.

(r x c)(r x c)

Multiplying Matrices

Determine if the matrices can be multiplied.

85

21

602

513

121

740

318

014

1.)

2.)

Operations Using Matrices

40

12AFind the product AB if

21

13B

Operations Using Matrices

085

142AFind AB if

1213

6084

4152

B

Operations Using Matrices

2

1

4

A

Do Now: Find the product AB if

102 B

Academy Algebra II/Trig12.4: Matrix AlgebraHW: p.889 (19, 20, 26 – on calc, 27 – on calc)

Identity Matrix

10

01

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.

100

010

001

Operations Using Matrices

310

021A

Suppose that

Find by hand and check your answers using your calculator.1.) 2.)

25

64

23

B

3AI 2BI

Input Matrices on TI-89 Calculator:1. Press APPS and select Data/Matrix2. Select 3: New3. Type– 2: Matrix, Folder– Main,

Variable– a4. Press ENTER, ENTER5. 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. **

Input Matrices on TI-83/84 Calculator:1. Press 2nd X-1 to select MATRX2. Arrow over to EDIT3. Select a matrix to edit4. Input the dimensions and # of the

Matrix.5. Repeat the steps above for matrix B. 6. Press 2nd 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.