1TTO §12.5 Quadratic formulas

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• Middelbare school
• havo, vwo
• Leerjaar 1

§12.5 Quadratic formulas

Ultra short recap and a look forward too:

+  §12.4 Linear formulas was about  STRAIGHT LINES. 

+ §12.5 Quadratic formulas is about  PARABOLAS.   

Graphs, graphs, graphs ...

As some graphs will be drawn by you in this paragraph,

now take before you:

+ Notebook 

+ Pencil, eraser and geo 

  

Remember your answer and key it in in the next slide.

Quadratic formulas are:

1. abcd
2. abc
3. abd
4. c

Solution:

As you've just learned, in order to be a Quadratic Formula,

there must be a SQUARE of a VARIABLE in it!

So this rings true for: a, b and d.

Formula c contains a square all right, but not the square of a variable!

Have you got a clue...

what the GRAPH for the FORMULA             = 

looks like?

Next 2 slides show you all about it.

And more! 

x​2​​

y

graph for:          =

y

x​2​​

Some points of attention for 

the graph of:            =

+ watch the nicely rounded shape

+ it's name is: a PARABOLA

+ some 'easy to find' points in the 

    table are: (3, 9), (1, 1) but also:

    (-3,9) and (-1,1)

y

x​2​​

So this graph for the formula:

y =            is ....

the BASIC QUADRATIC GRAPH!

In this paragraph you will

meet more quadratic graphs, that

are all variations to this one.

Next slide shows you a graph that is derived from (=afgeleid van) the

Basic graph.

x​2​​

Calculate y = x squared when x = -6

1. -36
2. 12
3. -12
4. 36

Solution:

y = 

when we fill in:  x = -6,  we need BRACKETS:

y =             = -6 x -6 = 36   (and not -36!)

Let's practice a bit more with this, as it will make doing

your homework easier!

x​2​​

(−6)​2​​

TASK: y =      - 3

Now when x = -4,

what is y ?

Remember and key in in the next slide!

x​2​​

1. -13
2. 5
3. -11
4. 13

SOLUTION:               y =      -3

Now when x = -4,  we replace the variable      by  -4, as follows:

y =            - 3  =            -3  =  -4  x  -4  -3 = 16 - 3 = 13

x​2​​

x

x​2​​

(−4)​2​​

Finally ...

You'll learn how to check if a certain point lies on a graph.

We will study the Method how to check this.

If this isn't clear to you, don't worry.

It's all in §12.5 and you can study the Method as long as you need!

Suppose you have a graph and a point ...

and you want to know IF that point lies on the graph.

What to do to know for sure?

Let's study the Theory in the next slide together.

Homework time

Remember to Study the Theory parts (again) when they come up!