Operations with Matrices:Multiplication

TSWBAT perform scalar multiplication; multiply to matrices

Scalar Multiplication

Scalar multiplication Multiplying a matrix by a real number Multiply each element by the real

number Just like distributing

-1 4

3 7

0 -8

5

-5 20

15 35

0 -40

Examples

3 -4

1 6

-4 5

7

4 5

-1 3

-2 8

-2

4 7

-3 52 +

0 -2

6 4

Class work

WB pg 23 1-6 Turn in when finished

Homework Worksheet

Multiplying Two Matrices

You can only multiply matrices if the columns of the first matrix have the same number of elements as the rows of the second matrix

-1 2

4 0

7 -5 3

1 6 8

2 x 2 2 x 3

2 x 3

Multiplying Two Matrices

Multiply the elements of each row of the first matrix by the corresponding elements in each column of the second matrix

Find the sum of each set of products

-1 2

4 0

7 -5 3

1 6 8

-1(7) 2(1) +

The answer goes in the corresponding spot, Row 1 Column 1

Example

-1 2

4 0

7 -5 3

1 6 8

-1(7) + 2(1) -1(-5) + 2(6) -1(3) + 2(8)

4(7) + 0(1) 4(-5) + 0(6) 4(3) + 0(8)

-5 17 13

28 -20 12

-7 + 2 5 + 12 -3 + 16

28 + 0 -20 + 0 12 + 0

Examples

3 -2

1 0

0 -5

6 8

4 3 1

0 -2

5 1

-3 6

7 1 2

-3 5 8

6 4

-2 -8

Using your Calculator

Push the green ALPHA button Push the zoom button Choose the dimensions of the

matrix, click OK Enter the numbers Choose the operations and repeat to

enter the second matrix If it says error, the 2 matrices cannot

be multiplied

Class work

WB page 24 14-18

Homework Worksheet