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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 103,721

Hi;

I will provide something in a few minutes.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**Au101****Member**- Registered: 2010-12-01
- Posts: 353

Oh of course - take your time - I hadn't meant for this thread to cause you - or anybody else - even more hard work.

*Last edited by Au101 (2011-07-21 09:17:41)*

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 103,721

Hi;

Now what you do is form a 6 x 6 set of simultaneous linear equations. This is done by substituting x = -3,-2,-1,0,1,2 in the above. That wipes out the x and you are left with:

Which is exactly what we expected.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**Au101****Member**- Registered: 2010-12-01
- Posts: 353

Oooh thanks bobbym that's perfect, my only question would be where we've accounted for the fact that the product of our denominators is four times the original denominator. I also wonder if it would be possible to tell that our numerators would be quadratics if we hadn't had the answer to begin with - more out of curiosity than anything else.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 103,721

Hi;

to tell that our numerators would be quadratics

One way is to say the numerator is an 8th degree poly, a quadratic times by a six degree

poly is an 8th degree poly.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**Au101****Member**- Registered: 2010-12-01
- Posts: 353

Oooh yes, that's very good - I'm still confused about that pesky four though

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 103,721

I think that is just some factor that Mathematica pulled out, for what reason... I do not know.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**Au101****Member**- Registered: 2010-12-01
- Posts: 353

Hmmm, yes I see, but ought we not account for it. I tried taking the four outside, although perhaps that was not correct. What I am interested in, though, is why we don't have to worry about it when computing *a,b,c,d,e* and *f*

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 103,721

Hi;

Because in the "fit" for the coefficients a,b,c,d,e,f it gets taken care of all by itself.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**gAr****Member**- Registered: 2011-01-09
- Posts: 3,479

Hi,

Shouldn't the partial fraction we expect be of the form:

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense" - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 103,721

Hi gAr;

That is two quadratics for the numerators also. Because

That is why I went right to 2 quadratics in the numerators.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**gAr****Member**- Registered: 2011-01-09
- Posts: 3,479

Hi bobbym,

Oh, okay!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense" - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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