1TTO §6.5 Comparing graphs PART TWO PTI

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• Middelbare school
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§7.5 Comparing graphs PART TWO

Many time a movie gets a sequel (=vervolg),

as in 'Home alone 2'.

The new one is not always better than the first film.

Let's hope for the best for this LessonUp ...

PART TWO ......

is about p.223 and 224 the 2nd part of  §7.5 Comparing graphs.

First let's look back at one Homework exercise:

number 33, p.223 is the one!

8

Task 1: Give your answer to 33a in the next slide.

Solution Task 1: (33a)

Task 1: Jean's better off ...

1. with Vital
2. it depends
3. with Hydro
4. this is not clear

Task 2:

Give your answer to 33b in the next slide.

Watch the vital word: 'INCREASE'!

Task 2: (33b) answer:

1. 225
2. 200
3. 35
4. 165

 Solution Task 2: (33b)

What is the number 200 doing in the calculation?

For more than 200 cubed metres Vital is cheaper. 

So, to explain it a little differently: for more than 165 + 35 = 200 cubed metres

Vital is cheaper, so the answer is:  a 35 cubed metres INCREASE!

We go on with 2 graphs in one coordinate system.

In PART ONE the emphasis (=nadruk) was on comparing them.

Now we concentrate on the POINT OF INTERSECTION (p.o.i) of both graphs! 

Task 3:

Read off the p.o.i. of both 

graphs.

Key in in next slide.

task 3: The p.o.i. is .......

1. (5, 4)
2. (3 1/2, 5)
3. (5, 3.5)
4. (5, 3 1/2)

Explanation Task 3:

Read off the p.o.i. of both 

graphs.

Key in in next slide.

Explanation: 

First we write down the HORIZONTAL

coordinate; only then the VERTICAL one.

So we get:  (5, 3  1/2)   or   (5, 3.5)   Don't forget the brackets!

There are 2 ways to get to know the points of intersection:

Reading off  p.o.i.      -         Calculating p.o.i.

But ...... when to do what?!

Why calculating, if you can read off ??!

Read below, why.

Many times the p.oi. from 2 graphs is hard to read off.

For instance:

you read off (3, 7) but in fact the p.o.i. turns out to be

(3.1 , 6,9) !

In fact CALCULATING is more exact -better- than reading off.

From READING OFF we now move to CALCULATING the p.o.i.!

Task 4:  Fill in number = 5 in the green formula.

The green graph has this formula:

6 - number x 0.5 = length

TASK 2:

On paper fill in number = 5 in this formula.

Take a pic of your CALCULATION and send it in, in the

next slide!

Fill in number = 5 in green formula.

Solution Task 4:  Fill in number = 5 in the green formula.

Task 5:  Fill in number = 5 in the red formula.

From the graph you can read off the red formula too:

number x 0.5 + 1 = length

TASK 3:

On paper fill in number = 5 in this formula.

Key in your CALCULATION in the next slide. 

Fill in 'number = 5'
in number x 0.5 + 1 = length

Explanation Task 5:  Fill in number = 5 in the red formula.

 The green formula :

number x 0.5 + 1 = length

Summarising (1)  what we just did:

Summarising (2):

Task 6: In order to do 35a and 36, what should you do first? Answer in next slide.

What to do first?

Solution Task 6:

Make a TABLE!

For 36a even make a DOUBLE TABLE,

 as there are 2 graphs!

Homework time