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Original poster

Algebra? Can anyone help with the answers to these questions?

27 replies

SecondhandRose · 16/01/2006 18:32

DS has done algebra homework in preparation for his 11+ on the 30th. Can anyone tell me if his answers are right please?

QUESTION ANSWER
9x + 1 = 5x + 9 4x =8 1x =2

9X - 11 = 3x + 13 6x =24 1x =4

6x - 5 = 4x + 7 2x = 12 1x =6

11x - 26 = 10x +18 1x = 46

12x - 16 = 7x-1 5x = 15 1x = 3

There are a few more for checking too!

OP posts:
Original poster
SecondhandRose · 16/01/2006 18:33

Oh, it's come out all squished together.
First one there should be a big space between the 9 and 4. Hope this makes sense to someone other than 10 and 11 year olds.

OP posts:
SoupDragon · 16/01/2006 18:34

I think the 4th one is x = 44

SoupDragon · 16/01/2006 18:35

others are right though.

JenumGeranium · 16/01/2006 18:37

Yes I agree - the others are right but no 4 is 44!

JenumGeranium · 16/01/2006 18:38

Call me sad but I quite enjoyed that!

SoupDragon · 16/01/2006 18:39

me too hehehe I used to love algebra!

Original poster
SecondhandRose · 16/01/2006 18:43

Thanks ever so much, how about these last few?

9x - 19 = 2x - 5
answer 7x=14 1x=2

7x +14 = 5x + 20
answer 2x=34 1x=17

9x +18 = 4x + 48
answer 5x=30 1x=6

11x +22 = 9x +36
answer 2x=14 1x=7

12x +12 = 7x +42
answer 5x=30 1x=6

OP posts:
Original poster
SecondhandRose · 16/01/2006 18:44

Any chance you can explain how to work them out?

OP posts:
Original poster
SecondhandRose · 16/01/2006 18:48

bump

OP posts:
JenumGeranium · 16/01/2006 19:06

Sorry - was having my tea!

Anyway back to business - number 2 isnt right I dont think but the others are.

How are they written before you have got the answer?

Jasnem · 16/01/2006 19:07

Please can someone tell me how to do these? I used to be good at maths, and have just discovered that I haven't a clue how to do algebra!

JenumGeranium · 16/01/2006 19:08

I can work them out if I am given the value of x - but only if it is right IYSWIM!

Jasnem · 16/01/2006 19:10

I can check that they are right, too, but it is really going to bug me that I can't actually work out the answer!

Jasnem · 16/01/2006 19:10

I can check that they are right, too, but it is really going to bug me that I can't actually work out the answer!

JenumGeranium · 16/01/2006 19:10

Yes I agree! There must be a way!

JenumGeranium · 16/01/2006 19:14

I think the answer to number 2 is 3.

Just through process of elimination! No formula that I have worked out!

SoupDragon · 16/01/2006 19:16

OK
7x + 14 = 5x + 20 so
7x - 5x = 20 - 14 so
2x = 6 so
x = 3

JenumGeranium · 16/01/2006 19:17

Ok I think I have it

make it 7x - 5x = 20-14

so 2x = 6 1x = 3

??????

Can see how you got 34 by putting 14 + 20.

SoupDragon · 16/01/2006 19:17

You swap the Xs and numbers across the sides so all the Xs are on one side of the = nd the numbers on the other(remembering that they switch sign when you move them across).

JenumGeranium · 16/01/2006 19:18

Hey I was right then SoupDragon!

I was determined to solve it!

SoupDragon · 16/01/2006 19:18

hehehe

MuddlingThru · 16/01/2006 19:21

To work it out:

You move all the x stuff to the left of the =, and all the absolute values to the right. As anything crosses sides it changes from + to - or vice versa. Then you will have a multiple of x = an absolute value. You then divide the absolute value by the multiple of x.

Does that make any sense?

Jasnem · 16/01/2006 19:21

Thankyou, I had just looked it up, but you both explained it brilliantly.

I just can't believe I had completely forgotten it all

MuddlingThru · 16/01/2006 19:21

oops x cross posted

Original poster
SecondhandRose · 16/01/2006 20:46

So out of the second lot I posted are they all right except 7x + 14 ?

Thanks - it's too late, I'm not capable of working them out myself.

OP posts: