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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: 88,621

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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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: 88,621

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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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: 88,621

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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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: 88,621

Re: Simple subtracting square roots? Not to me!

I am getting


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 15,600

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: 88,621

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

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

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 15,600

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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