# 2TH §5.1 Removing single brackets

1. Calculate the perimeter of the figure. Write your answer as short as possible.

2. Calculate the area of the figure. Write your answer as a single square root.
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Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 2

In deze les zitten 19 slides, met tekstslides.

Lesduur is: 50 min

## Onderdelen in deze les

1. Calculate the perimeter of the figure. Write your answer as short as possible.

2. Calculate the area of the figure. Write your answer as a single square root.
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#### Slide 1 -Tekstslide

Starting with something new
Removing single brackets
Something like this .....  5(2+4)  =

#### Slide 2 -Tekstslide

Removing single brackets
5(2+4)=

11                                   -1

30                                 something else

#### Slide 3 -Tekstslide

Rectangles
You can think of the calculation 5(2+4) as working out the area of this rectangle.

#### Slide 4 -Tekstslide

Rectangles
The area of the rectangle is
length x width =
5 x (2+4) =
5(2+4)

#### Slide 5 -Tekstslide

Rectangles
area rectangle = 5(2+4) = 5 x 6 = 30

You could also calculate the area of the
blue rectangle and red rectangle first
area rectangle = 5 x 2 + 5 x 4 =
10 + 20 = 30

#### Slide 6 -Tekstslide

Rectangles with variables
If at least one of the sides of the rectangle is given as a variable, you can make a formula for the area of the rectangle.

#### Slide 7 -Tekstslide

Rectangles with variables
You can make a formula with brackets and one without.

Area rectangle = 5 x (t+4) = 5(t+4)
OR
Area rectangle = 5 x t + 5 x 4 =
5t + 20

#### Slide 8 -Tekstslide

Rectangles with variables
Because both formulas give the same area, we now now that
5(t+4) = 5t + 20

We can use this to rewrite formulas
with brackets as formulas without
brackets.

#### Slide 9 -Tekstslide

Removing brackets
Write the formula y = 2(3t + 4) without brackets.

#### Slide 10 -Tekstslide

Removing brackets
Write the formula y = 2(3t + 4) without brackets.
Think of a rectangle with a side of 2 and a side of 3t + 4

#### Slide 11 -Tekstslide

Removing brackets
Write the formula y = 2(3t + 4) without brackets.
Think of a rectangle with a side of 2 and a side of 3t + 4
Area blue rectangle = 2 x 3t = 6t
Area red rectangle = 2 x 4 = 8

y = 6t + 8

#### Slide 12 -Tekstslide

Removing brackets
Instead of a rectangle, you can also use a multiplication table.

y = 2(3t + 4) = 6t + 8

#### Slide 13 -Tekstslide

More variables, negative numbers
If you want to write 2t(5t - 3) without brackets, it is hard to imagine a rectangle, because a lenght of -3 is not possible.
We can still  use a multiplication table!

#### Slide 14 -Tekstslide

More variables, negative numbers
Write y = 2t(5t - 3) without brackets.

What should be written over here?

7t
10t
7t2
10t2

#### Slide 15 -Tekstslide

More variables, negative numbers
Write y = 2t(5t - 3) without brackets.

What should be written over here?

t
6t
6t
2t3

#### Slide 16 -Tekstslide

More variables, negative numbers
Write y = 2t(5t - 3) without brackets.

#### Slide 17 -Tekstslide

Notation
If a 1 is written in front of a variable or bracket, you do not write down the 1.

Instead of 1p, you write p
Instead of -1t, you write -t
Instead of -1(5t+2), you write -(5t+2)

#### Slide 18 -Tekstslide

Homework Tuesday
§5.1 Do exercises S4, 4, 5, S6 and 6
Don't forget to check and correct your answers with the solutions book!