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#1 2013-03-23 22:26:20

Gazzer
Member
Registered: 2013-03-23
Posts: 5

Simple subtracting square roots? Not to me!

Hi,
In the attached image the highlighted subtraction has me stumped. I just can't see how the answer could be (1-sqrt(7))x^2.

I would be very grateful if someone could explain how this is so.

Thanks.

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#2 2013-03-23 22:26:56

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 86,219

Re: Simple subtracting square roots? Not to me!

Hi;

I do not see any image.


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#3 2013-03-23 22:29:59

Gazzer
Member
Registered: 2013-03-23
Posts: 5

Re: Simple subtracting square roots? Not to me!

Ha! I can't get that to work either!

As part of a polynomial long divisio is a subtraction  -6x^2 - sqrt(7)(1-sqrt(7)x^2) the answer is (1-sqrt(7))x^2

I don't understand!

Last edited by Gazzer (2013-03-23 22:34:52)

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#4 2013-03-23 22:31:41

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 86,219

Re: Simple subtracting square roots? Not to me!

Hi;

- -6x^2

What is that?


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#5 2013-03-23 22:35:37

Gazzer
Member
Registered: 2013-03-23
Posts: 5

Re: Simple subtracting square roots? Not to me!

Sorry, I'm rushing. I have to take my wife to London in a minute! I've edited the original.

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#6 2013-03-23 22:39:39

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 86,219

Re: Simple subtracting square roots? Not to me!

Hi;

Is that the problem?


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#7 2013-03-23 22:40:16

Gazzer
Member
Registered: 2013-03-23
Posts: 5

Re: Simple subtracting square roots? Not to me!

Yes. That's it.

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#8 2013-03-23 22:40:47

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 86,219

Re: Simple subtracting square roots? Not to me!

I am getting


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

Online

#9 2013-03-23 22:41:13

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 15,518

Re: Simple subtracting square roots? Not to me!

So, I am guessing that you need to know why the remainder is 1-sqrt(7)x^2 in a certain polynomial long division?

Last edited by anonimnystefy (2013-03-23 22:42:36)


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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#10 2013-03-23 22:50:07

Gazzer
Member
Registered: 2013-03-23
Posts: 5

Re: Simple subtracting square roots? Not to me!

Bobbym :- I think I misled you. it should be -6x^2-(sqrt(7))(1-sqrt(7))x^2
anonimnystefy - yes.

Thanks for your help. I have to go now. I'll be back this evening.

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#11 2013-03-23 22:52:28

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 86,219

Re: Simple subtracting square roots? Not to me!

I am afraid then that their answer is correct!


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

Online

#12 2013-03-23 22:54:44

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 15,518

Re: Simple subtracting square roots? Not to me!

I think we will need more details, so, see you then.


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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