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#1 2012-11-27 07:38:10

BarandaMan
Guest

How do you solve three equations in three unknowns?

Equation 1 has p1 and p3 in.
Equation 2 has p2 and p3 in.
Equation 3 has p1, p2 and p3 in.

This is highest priority in terms of my work as I think it will help me solve one of the other questions I have posted up. Will refresh every 5 minutes so am here to discuss! big_smile Thanks you all

#2 2012-11-27 07:38:44

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

What are the equations?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#3 2012-11-27 07:41:53

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

Will it be easier if I right in neat on paper and then upload picture for you bobby? Or easier for you if I write on here in the (messy) way?:P

#4 2012-11-27 07:46:57

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Hi;

Post it here. Use lots of spaces for clarity and brackets.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#5 2012-11-27 07:52:57

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

(4 - P3) /2 = P1
(6 - P3) /2 = P2
P3 = (10 - 0.5P1 - 0.5P2) / 2

i47.tinypic.com/97vbwk.jpg - JUST incase my writing is uncomprehendable!


What I have tried is to put the expression for P3 into the first equation, this led me to get P2=3P1+12
I then tried to put the expression for P3 into the second equation, this led me to get P1=3P2+8

I then P1=3P2+8 into P2=3P1+12 and I got from this, that P2=-4.5? Which is wrong I assume only because the question specified P>0 (since P= price), so I must have gone wrong I think!

#6 2012-11-27 08:04:10

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Hi;

Is the the system you want solved?

P1 = - ( 1 / 2 )

P2 = 1 / 2

P3 = 5


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#7 2012-11-27 09:40:44

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

Oh my god?! How did you do that? This is incredible. Apologies for the delayed response, internet went down for over an hour.

#8 2012-11-27 09:43:04

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Hi;

Do you know how to use substitution?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#9 2012-11-27 09:44:00

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

bobbym wrote:

Hi;

Do you know how to use substitution?

I think so, that's what I tried but I always got it wrong!

#10 2012-11-27 10:03:10

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Did you use equation 1 and substitute for P1 into equation  3?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#11 2012-11-27 14:58:12

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

bobbym wrote:

Did you use equation 1 and substitute for P1 into equation  3?

I tried substituting everything into everything, I keep going round in circles and have two unknowns in every equation. But this can be done apparantly it shouldn't be too difficult. I just cannot see it. sad

#12 2012-11-27 15:08:23

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Hi;

From the first equation you get

You substitute for P1 in equation 3. That gives 2 equations with 2 unknowns. Can you solve now?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#13 2012-11-27 15:09:34

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

Wait I think I just did it, i got p1 = -1/2. We cannot have a negative price so I won't solve for p2 and p3 yet, I must have done something wrong earlier. This is awful I will not be asleep for a while.

#14 2012-11-27 15:11:06

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

P1 = ( - 1 / 2 ). If that does not fit then you have set the problem up wrong.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#15 2012-11-27 15:16:00

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

THANK you for guiding me on this. Please don't waste your time here, I will go over this freshly again and see what I have done wrong. I HAVE to get to a stage with three equations in three unknowns, it just means my numbers were wrong earlier because a negative price cannot happen in this particular question, but thanks to you at least i can solve three equations in three unknowns! tongue

Maths is SO stressful sometimes and i try SO hard, i am really good at mental maths but as you can see I am poor at most else, it really drags because i want to do well. sad tongue thank you again for your help bobby.

#16 2012-11-27 15:20:19

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Hi;

Maths is SO stressful sometimes and i try SO hard,

Math is hard work for everybody. Go over how you set the problem up there is certainly a mistake there.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#17 2012-11-28 06:42:37

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

DONE IT!!!

Basically, I missed out a '2p2' a LOT earlier on, I went through it all over and wrote it again and I was like, where did that 2p2 dissappear?! (I forgot it off one line of algebra)...went through everything and the end three equations were very simple thanks to your guidance. Thank you again. LOVE it when it works!

#18 2012-11-28 07:36:02

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Your work looks like you are doing some kind of physics. You have my sympathy...


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#19 2012-11-28 08:03:51

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

I am doing a bit of EVERYTHING! tongue
What did you specialise in??

#20 2012-11-28 08:12:36

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: How do you solve three equations in three unknowns?

Unfortunately at one time I loved physics and group theory. I actually thought I was doing mathematics... Then like Saul, I was struck by lightning and saw the light. Computational mathematics!


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#21 2012-11-28 08:25:13

BarandaMan
Guest

Re: How do you solve three equations in three unknowns?

bobbym wrote:

Unfortunately at one time I loved physics and group theory. I actually thought I was doing mathematics... Then like Saul, I was struck by lightning and saw the light. Computational mathematics!

Hahahaha! That is brilliant! tongue

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