# 2Tvwo § 3.5 Cubic roots '19'20

§3.5 Cubic roots
First we look back at §3.4 Simplifying fractions.

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Slide 1: Tekstslide
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In deze les zitten 20 slides, met interactieve quizzen en tekstslides.

Lesduur is: 50 min

## Onderdelen in deze les

§3.5 Cubic roots
First we look back at §3.4 Simplifying fractions.

18
timer
0:32
Simplify

#### Slide 2 -Woordweb

solution:
=              x                    =        3     x                      =   3

18
9
2
2
2

72
timer
0:43
Simplify:

#### Slide 4 -Woordweb

Solution:
There are more possibilities, but we always search for the LARGEST square root. So:
=                x              =   6  x               =    6

72
36
2
2
2

#### Slide 5 -Tekstslide

§3.5 Cubic roots
We will compare the new thing -Cubic root- with
the Square root, that is well-known to you by now!

#### Slide 6 -Tekstslide

Cubic roots
We could think of square roots
as the length of the sides of a
square if you know the area.

In the same way, cubic roots
can be thought of as the length of the sides of
a cube if you know the volume.                                 Volume cube    = 3 x 3 x 3
= 27
33

ANS

#### Slide 10 -Tekstslide

The edges are .... cm long.

#### Slide 12 -Tekstslide

Once more: a cubic root belongs to a cube!
When you know the volume, then the length, width and height are
the cubic root of the volume!

#### Slide 13 -Tekstslide

Watch this big difference between square roots and cubic roots:
√(-100)        does not exist, because there is no number that, when squared,
becomes -100.     However ...........
∛(-1000)  DOES exist!
Because:             -10 x -10 x -10 = -1000
So the Cubic Root of -1000 is -10.
Or:    ∛(-1000) = -10

#### Slide 14 -Tekstslide

Cubic roots
Unlike square roots, it is possible to take the cubic root of a negative number, because a negative number raised to the third power is negative!

#### Slide 15 -Tekstslide

Calculate (without a calculator)

31000=

#### Slide 16 -Open vraag

Exact or approximation
If you try to calculate                  on your calculator
(use shift + the button shown on the right)
you will get the result -2.5198421
This number is an approximation to 7 decimal places.
If you round off to -2.52 it is an approximation to
2 decimal places.
is an exact value.
316
316

#### Slide 17 -Tekstslide

This KEY you need to use:
Key in:
SHIFT + the key
shown here.
Then you take the
CUBIC ROOT or
THIRD ROOT
of 64, which is 4.

#### Slide 18 -Tekstslide

Use your calculator to give an approximation accurate to 3 decimal places of
328

#### Slide 19 -Open vraag

Homework Tuesday
• Make and correct the exercises from §3.5 (support, standard or challenge).
• Finally send in pics of your work in GC again!
• you may skip 32