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#1 2011-04-14 23:16:56

Marisca
Guest

Applications of polynomials

Hi, I've been studying for a test and I came across this question  http://i473.photobucket.com/albums/rr92 … ki/001.jpg
where I was asked to state the value of 'b'
I've been trying to solve it, but so far, I've had no luck. I was wondering if anyone would be willing to help me.

#2 2011-04-14 23:45:09

TheDude
Member
Registered: 2007-10-23
Posts: 361

Re: Applications of polynomials

You're given 3 points on this line, (0,0) (1,0.9) (10,0).  You can use those to determine a and b.

Wrap it in bacon

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#3 2011-04-15 00:34:16

Marisca
Guest

Re: Applications of polynomials

I understand that, but I don't exactly know how to put those points into the equation to find a and b.

#4 2011-04-15 05:07:20

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Hi Marisca;

If you are trying to fit to that equation. First I must ask, do you agree with these 3 points (0,0) (1,0.9) (10,0)?

Boy do I love school problems! In the real world a problem like this is a big pain in the neck. But those school problems just make it so easy!!

Set up the simultaneous equations that look like this:

Manipulate to:

Ordinarily we would have a problem with that non linear term. But magically it is easy here. Times the top equation by -100.

Add em up!

Substitute a into the first equation on top and get:

Your equation is:

This is tentative. There are two more conditions that this equation must satisfy. It must pass through the point (0,0) and the slope at (0,0) must be 0. Can you do these or do you need help?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#5 2011-04-15 12:29:53

Marisca
Guest

Re: Applications of polynomials

Thank you so much, I finally get it.
I think I know how to do the rest of it too. I'm glad that you enjoyed solving it.

#6 2011-04-15 14:35:03

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Hi Marisca;

Welcome to the forum.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#7 2011-04-21 21:02:55

Marisca
Guest

Re: Applications of polynomials

Thanks for welcoming me. I should really get an account here.

I actually have another question, it continues on from the first question I asked.
http://i473.photobucket.com/albums/rr92 … ki/003.jpg
All I understand so far (possibly) is that I need to use the equation I got from the first question and this one.
But I'm having trouble working with them both. Anyone willing to lend a hand?

#8 2011-04-21 21:07:01

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Hi Marisca;

I cannot see that jpeg. It is tiny!

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#9 2011-04-21 21:15:42

Marisca
Guest

Re: Applications of polynomials

Really? It turns out big on my computer.
Here, try this link

http://i473.photobucket.com/albums/rr92 … /003-1.jpg

#10 2011-04-21 21:31:42

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Hi;

It is only showing one equation. I need the other one too!

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#11 2011-04-21 21:37:59

Marisca
Guest

Re: Applications of polynomials

The other equation is
y=-1/10x^2(x-10)

#12 2011-04-21 21:45:32

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Hi;

Do you mean this:

There are 3 solutions to that set of equations:

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#13 2011-04-21 21:50:42

Marisca
Guest

Re: Applications of polynomials

Yes, sorry I should have made it more clear.

#14 2011-04-21 21:53:16

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Solution is up there!

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

#15 2011-04-21 22:09:13

Marisca
Guest

Re: Applications of polynomials

Thanks, but I don't really understand what you did there. Could you show the working out?

#16 2011-04-21 22:12:55

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

What part do you need to understand?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

#17 2011-04-21 22:20:06

Marisca
Guest

Re: Applications of polynomials

How do you get the coordinates for P and Q from the 3 solutions?

#18 2011-04-21 22:22:13

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Coordinates are just x and y values paired together.

First set of coordinates are:

Second set of coordinates are:

Can you get the third set (Q) of coordinates now? Do you see how it is done?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

#19 2011-04-21 22:26:26

Marisca
Guest

Re: Applications of polynomials

Thank you!
I can't believe that I didn't think of subbing the equations into each other.

#20 2011-04-21 22:28:47

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Did you get the third set of coordinates?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

#21 2011-04-21 22:37:44

Marisca
Guest

Re: Applications of polynomials

Yes

#22 2011-04-21 22:40:18

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Applications of polynomials

Okay, then you are done. Please consider registering.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

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