Math Is Fun Forum

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.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Simple subtracting square roots? Not to me!

Hi;

I do not see any image.

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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.

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)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

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.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

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.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Gazzer

Member

Registered: 2013-03-23

Posts: 5

Re: Simple subtracting square roots? Not to me!

Yes. That's it.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Simple subtracting square roots? Not to me!

I am getting

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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.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

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)

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“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
The knowledge of some things as a function of age is a delta function.

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.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

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.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Simple subtracting square roots? Not to me!

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

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“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
The knowledge of some things as a function of age is a delta function.