Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

Matrix Multiplication Day 1

I can...~ determine if two matrices can be multiplied~ multiply matrices without a calculator

Please take our your homework.

Agenda:• ACT Tips• Go over HW• Lesson• Exit Slip

Unit 8: Matrices

2/1

2/2

2/3

2/4

2/5

2/8

2/9

2/10

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

Some general ACT tips: • Dress in layers. You know how rooms here can be warm

or cold. You will test better if you are comfortable.

• You can bring a snack or something to drink for break

time but you will NOT be allowed to have them in the testing room.

• Bring or wear a watch. There will be no countdown timer projected. Just an end time posted on the board and a 5 minute warning. And you won't be able to check the time on your phone!

• Do not worry if you don't know everything...just do your best!

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

Are you ready to multiply???

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

In order to multiply two matrices,the inside dimensions must match.

ex)  If [A] is 2x3            [B] is 3x6, can we multiply them?

• the resulting matrix will have the outside dimensions. 2 x 6

YES!erase

erase

Matrix Multiplication• multiply each row in the first matrix by each column in the second matrix.

• Add up all the products of a row times a column, and it will give you one entry in the result matrix.

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

This is for the top row

22 38 44

This is for the bottom row

29 50 58

We are multiplying a 2x2 times a 2x3. The middle numbers match, so our resulting matrix will be 2x3.

So the resulting matrix will be:

erase

erase

* = multiplication

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

3 0 ­1 .5 2

16­4

0=

The dimensions of this are 1x3 times 3x2 so the resulting matrix will be a 1x2.

Multiply these matrices...

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

Multiply these matrices...

3­1 711

158 20­56

Can I add or multiply these? why or why not?

1­56

134

9 8

08

­27

6

Need to

be t

he sa

me

dimensio

ns!

Middle dimensions

need to match!

No

Yes

Yes

No

No

Yes

Yes

No

No

No

No

No

3x2

3x2

2x2

3x2

Sometimes the order of the matrix multiplication can be reversed...for example: If A*B doesn't work, you can change it to B*A.

lots of erasing on this page

erase

erase

erase

erase

eraseerase

Unit 8 Day 2 Multiplying Matrices Day 1 lesson.notebook February 02, 2016

Homework:

Matrix Worksheet #2

Exit slip:

Given matrices A, B, and C below, find the following...

1) A+B 2) 2A-C 3) (A)(B) 4) (B)(C)