# 2TH §5.2 Removing double brackets

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Slide 1: Slide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 2

This lesson contains 16 slides, with interactive quiz and text slides.

Lesson duration is: 50 min

## Items in this lesson

Entry ticket
timer
6:00

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#### Slide 2 -Slide

Which exercises/theories should we discuss on the board?

#### Slide 3 -Mind map

Today's program
Questions about the homework? §5.1 exercises S4, 4, 5 and 6
Refresh: Removing single brackets
New theory: Removing double brackets

#### Slide 4 -Slide

Removing single brackets
In §5.1 you learned how to write a formula such as y = 2t(3t + 4) without brackets, by thinking of the formula as the area of a rectangle with a side of 2t and a side of 3t + 4.
You could also work this out with a multiplication table or by drawing arcs.
Rectangle                             Multiplication table             Arcs

#### Slide 5 -Slide

• Draw arcs to show what multiplication you're doing.
• Work this out on a peace of paper and give it to your teacher
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3:00

#### Slide 6 -Slide

Removing double brackets
In the same way, you can write formulas such as y = (2t + 3)(3t + 4) without brackets. Think of a rectangle with a side of 2t + 3 and a side of 3t + 4.

#### Slide 7 -Slide

Removing double brackets
What should be written in the
blue rectangle?

I don't know
5t
6t
5t2
6t2

#### Slide 8 -Slide

Removing double brackets
What should be written in the
green rectangle?

I don't know
6t
9t
6t2
9t2

#### Slide 9 -Slide

Removing double brackets
The area is

So
can be written without brackets as

#### Slide 10 -Slide

Removing double brackets

When removing brackets from formulas with negative numbers, you can use a multiplication table. Example: y = (2n - 7)(n + 1)
Put the 2n and -7 in the left column and n and 1 in the top row.

#### Slide 11 -Slide

Removing double brackets

When removing brackets from formulas with negative numbers, you can use a multiplication table. Example: y = (2n - 7)(n + 1)
Put the 2n and -7 in the left column and n and 1 in the top row.
Fill in the table.

#### Slide 12 -Slide

Removing double brackets

When removing brackets from formulas with negative numbers, you can use a multiplication table. Example: y = (2n - 7)(n + 1)
Put the 2n and -7 in the left column and n and 1 in the top row.
Fill in the table.      Write the formula as short                                                                                 as possible.

#### Slide 13 -Slide

Removing double brackets
You can draw arcs to show what multiplications you are doing. This is sometimes called the "parrot beak" method (do you see the shape?).
Example:

#### Slide 14 -Slide

Which method should I use?
When being asked to write a formula without brackets, you can choose which method you use (rectangle, multiplication table, arcs, or something else).
You do not have to show how you removed the brackets, but a rectangle/table or steps will show you know how to remove brackets, even if you make small mistakes.

#### Slide 15 -Slide

HW Tuesday
§5.2 Do exercises 9, 11, 12 and 13b
Don't forget to check and correct your answers with the Solutions book