2Tvwo § 3.5 Cubic roots '19'20

§3.5 Cubic roots
First we look back at §3.4 Simplifying fractions.
Here comes your exit-ticket!

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§3.5 Cubic roots
First we look back at §3.4 Simplifying fractions.
Here comes your exit-ticket!

Slide 1 - Diapositive

18
Simplify

Slide 2 - Carte mentale

solution:
=              x                    =        3     x                      =   3    

18
9
2
2
2

Slide 3 - Diapositive

§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 4 - Diapositive

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             because        = 9                                                                                                                                                                                       because
of the sides of a cube if you know the volume.                                     = 3 x 3 x 3 = 
                                                                                                                                      = 27   
33
32

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Slide 7 - Diapositive

A task for the Taskforce (that is YOU!)
ANS

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The edges are .... cm long.

Slide 9 - Carte mentale

Slide 10 - Diapositive

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!

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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 12 - Diapositive

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 13 - Diapositive

Calculate (without a calculator)

31000=

Slide 14 - Question ouverte

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 15 - Diapositive

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

Slide 16 - Question ouverte

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

Slide 17 - Diapositive