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

-1
5 3
0
Just like distributing
4
-5
20
7
15
35
-8
0
-40
Examples
3
-4
7 1
-2
6
-4
5
2
4
7
-3
5
+
4
5
-1
3
-2
8
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
7
-5
3
4
0
1
6
8
2x2
2x3
2x3
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
7
-5
3
4
0
1
6
8
-1(7) + 2(1)
The answer goes in the corresponding
spot, Row 1 Column 1
Example
-1
2
7
-5
3
4
0
1
6
8
-1(7) + 2(1) -1(-5) + 2(6)
-1(3) + 2(8)
4(7) + 0(1)
4(3) + 0(8)
4(-5) + 0(6)
-7 + 2
5 + 12
-3 + 16
-5
17
13
28 + 0
-20 + 0
12 + 0
28
-20
12
Examples
4
3
-2
0
-5
1
0
6
8
3
1
0
-2
5
1
-3
6
7
1
2
6
4
-3
5
8
-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