Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

Login

Username

Password

Not registered yet?

#1 2013-03-24 21:26:20

Gazzer
Novice

Offline

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.

#2 2013-03-24 21:26:56

bobbym
Administrator

Online

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 have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#3 2013-03-24 21:29:59

Gazzer
Novice

Offline

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 (2013-03-24 21:34:52)

#4 2013-03-24 21:31:41

bobbym
Administrator

Online

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 have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#5 2013-03-24 21:35:37

Gazzer
Novice

Offline

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.

#6 2013-03-24 21:39:39

bobbym
Administrator

Online

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 have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#7 2013-03-24 21:40:16

Gazzer
Novice

Offline

Re: Simple subtracting square roots? Not to me!

Yes. That's it.

#8 2013-03-24 21:40:47

bobbym
Administrator

Online

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 have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#9 2013-03-24 21:41:13

anonimnystefy
Real Member

Offline

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 (2013-03-24 21:42:36)


The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

#10 2013-03-24 21:50:07

Gazzer
Novice

Offline

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.

#11 2013-03-24 21:52:28

bobbym
Administrator

Online

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 have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#12 2013-03-24 21:54:44

anonimnystefy
Real Member

Offline

Re: Simple subtracting square roots? Not to me!

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


The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

Board footer

Powered by FluxBB