1Tvwo §11.5 Quadratic formulas

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• Middelbare school
• havo, vwo
• Leerjaar 1

§11.5 Quadratic formulas

+  §11.4 Linear formulas was about  STRAIGHT LINES. 

+ §11.5 Quadratic formulas is about  PARABOLAS (?!)

    When following this LessonUp you will learn what

    this is. 

Graphs, graphs, graphs ...

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

now take before you:

+ your Notebook 

+ a pencil, eraser and geo 

In other words: The Right Stuff.     

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:          =

This is the 'Mother' of all

Quadratic Graphs!

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​​

 This GRAPH for the formula:

y =            is ....

the BASIC QUADRATIC GRAPH!

In this paragraph you will

meet more quadratic graphs, that

are all variations of this one.

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

Basic graph.

x​2​​

Task:

What is the main difference 

between this graph and the one

for                                           ?

y=x​2​​

Now follow a few tasks to ...

give you the neccessary practice for doing the

Homework.

Calculate
when x = -6

y=x​2​​

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:       

Now when x = -4,

calculate 

Remember and key in, in the next slide!

y=x​2​​−3

y

Calculate
, when

y=x​2​​−3

x=−4

1. -13
2. -7
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 later this lesson.

For this we will use the Method on p.192.

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?

This is not about READING OFF from a graph, but about CALCULATING!

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

Homework time

Do: §11.5 Quadratic formulas: choose your learing path

Check your answers with the solutions book in Teams!