# 1TH/vwo §12.1 Addition and subtraction

Ch 12 Calculating with variables
Today we do:
so:   +   and    -
By the way: we do more than 2 exercises from §12.1 now, in this LessonUp.
Pay attention well and you don't have to make them on paper any more!
1 / 25
Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

In deze les zitten 25 slides, met interactieve quizzen en tekstslides.

Lesduur is: 45 min

## Onderdelen in deze les

Ch 12 Calculating with variables
Today we do:
so:   +   and    -
By the way: we do more than 2 exercises from §12.1 now, in this LessonUp.
Pay attention well and you don't have to make them on paper any more!

#### Slide 1 -Tekstslide

You can shorten a formula .....
By adding " Like terms" together
or by subtracting " Like terms" from each other
But what are like terms?
They are the terms that have the same variables.
By the way, 'just numbers', so without any variables, are also like terms:
8 + 9 = 17  Here 8 and 9 are like terms that you can add together.

#### Slide 2 -Tekstslide

Examples
h = 4r + 2r  there are 2 terms both with variable r
so adding them gives h = 6r

b = 2a + 7a -10 here there are 3 terms but only 2a and 7a are like terms
so we get      b = 9a -10

p = 4 + 6 + 2s
p = 10 + 2s ( we cannot add 10 to 2s)

#### Slide 3 -Tekstslide

A few tasks for you ...

Shorten:
k = -4 + 6k -6
timer
0:20
A
k = 10 + 6k
B
k = 6k - 10
C
k = -10 + 6k
D
k = 16k

#### Slide 5 -Quizvraag

Solution:
k = -4 + 6k -6         The like terms are the terms we like.
The like terms here are -4 and -6.
k = -10 + 6k    or  also:    k = 6k - 10
Attention: in 'Ch9 Negative numbers' you                                                                             learned that -4 -6 = -10
however:      -4 x -6 = 24 (so: positive!)

#### Slide 6 -Tekstslide

t = -5k - 5 + 3k + 7
Shorten again!
timer
0:25
A
t = 2k + 2
B
t = -2k + 2
C
t = -2k - 2
D
t = -4k

#### Slide 7 -Quizvraag

Solution:
t = -5k - 5 + 3k + 7              Taking the like terms together gives:
t = -2k + 2
Finally: -2k and 2 are not like terms,
so you cannot add them together.

timer
0:30

#### Slide 9 -Tekstslide

A possible solution:

#### Slide 10 -Tekstslide

Now answer 1b in the next slide!

#### Slide 11 -Tekstslide

timer
0:30
P = 20 + b+ b + 20 + b + b + 20 + b + b + 20 + b + b

Solution:

High time ...
for a Joke.
Don't ya think?!

#### Slide 14 -Tekstslide

We do exercise 6, which saves you some homework.
It isn't an easy one (and that is why we do it together!).
So participate and learn.

#### Slide 16 -Tekstslide

1st. Open your Notebook and get a pen or pencil.
timer
0:45

SOLUTION a:

timer
1:00

#### Slide 19 -Tekstslide

The formula for Rose and Cindy together is:
A
s = 8m + 12.50
B
s = 20.50m
C
s = 12.50m + 8
D
s = 20.50

Solution b:

#### Slide 21 -Tekstslide

FOTOVRAAG!
WORK OUT, SOLVING AN EQUATION, AS YOU LEARNED IN CH10!

#### Slide 22 -Tekstslide

95.50 euros both have saved.
After how many months?
timer
1:00

#### Slide 23 -Open vraag

the Formula:
s = 12.50m + 8
After how many months did they save 87.50 euros?

SOLUTION c:

#### Slide 24 -Tekstslide

Homework:
There are only 4 exercises left:
+  H and H/V:    2, 3, 4, 5 and S5
(Opting for VWO? You'd better do VWO then, see below!)
+  VWO:  Challenge path, do:
3, 4, 5, and C1, C2
+ Good luck!