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#226 2013-08-04 10:42:12

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 14,819

Re: Simplify the following:

Something is wrong there. Are you sure you copied the problem correctly?


“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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#227 2013-08-04 17:46:19

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

log(y^2/2x) = log2y-log2x

The right hand side of that is incorrect.


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.

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#228 2013-08-05 01:02:51

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

it's log2(y-x)

I multiplied log2 with what is in the bracket, to have that. Why you say so.

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#229 2013-08-05 01:05:55

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Hi;

Because when you write

log2y-log2x

how do you know which of these is what you want

log(2)*y or log(2y)?


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.

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#230 2013-08-05 01:36:17

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

Errr, I dont normally put bracket around figures as you normally do.
But I suppose each of them are the same, I mean what yours above.
In #229

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#231 2013-08-05 01:39:18

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Errr, I dont normally put bracket around figures as you normally do.

Math has to be precise. More precise than anything else you do.

When you write log2x, no one can figure out what you mean. It appears you wanted log(2)x, but I am not sure. Which do you want?


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.

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#232 2013-08-05 02:07:39

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

Thanks, Bobbym.

Then please let me how it should be

By the way I have developed the attitude of not putting brackets c'os the book I have doesn't put it around each example it gives. And that has become of me.

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#233 2013-08-05 02:09:24

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Hi;

In post #225 you wrote this

log(y^2/2x) = log2y-log2x

Please use brackets to tell me what you want on the right hand side.


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.

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#234 2013-08-05 02:21:11

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

But Bobbym I havent envisioned that bracket of the right hand side could cause any thing, but I think;

Log2(y-x) = log2y-log2x

I think is the same as, log(2y)-log(2x)

Please help if I am confused.

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#235 2013-08-05 02:34:07

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Okay, we have the original problem looking like this

If 2logy-log2x=2log(y-x), express y in terms of x. I had (y-x)(y-2x^2). The book has y^-4xy+4^2x=0.

Hold on while I work on it. The book answer is okay but it is not an answer to the question


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.

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#236 2013-08-05 02:45:03

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

Oops. Bobym.
Please I made a little blunder!

2logy-log2x=log2(y-x).

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#237 2013-08-05 02:52:07

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

So you want this?

It looks a lot like the earlier one.


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.

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#238 2013-08-05 03:45:39

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

2logy-log2x=log2(y-x)
express y in terms of x.

This how is in the book.


Thanks.

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#239 2013-08-05 03:47:40

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

That book is awful.

Mathematics uses brackets to avoid ambiguities.

I will interpret it as:


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.

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#240 2013-08-05 03:57:53

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

But is the answer I had the same as yours when you solved?

I am using my phone to browse and the battery has run low.

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#241 2013-08-05 03:59:39

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Those are all correct answers with methods shown.


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.

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#242 2013-08-05 04:11:35

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

Is your interpretation the ones the book should have used?

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#243 2013-08-05 04:18:05

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Let's see what happens.

10^ to both sides

Multiply both sides by 2x


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.

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#244 2013-08-06 21:15:57

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

anonimnystefy wrote:

Hi EbenezerSon

With a careful look at signs I think should be,
x-3x-3-3/x^2-9 =

-2x-6/x^2-3^2 =

-2(x+3)/(x-3)(x+3)
= -2/x-3

Please am I right there.

Thanks.

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#245 2013-08-07 04:02:18

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

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.

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#246 2013-08-07 23:50:27

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

Oops,

I have considered it once more and I could see Anonymstify is right with his answer, I  lost sight with some negative sign, here

x+3-3(x-3) = x+3-3x+3.
=-2x+6

Bobbym, I suppose you lost sight on a negative sign. With a careful check you will adentify it.

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#247 2013-08-08 00:08:30

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:

Hi;

I am sorry but my answer is correct.

Please check post #244, in line 2 there is an error.


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.

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#248 2013-08-08 00:51:34

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

Please could you demostrate to me?,  c'os I can't adentify it.

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#249 2013-08-08 00:55:49

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,501

Re: Simplify the following:


How did 3(x+1) become 3x-3?


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.

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#250 2013-08-08 01:23:00

EbenezerSon
Member
Registered: 2013-07-04
Posts: 230

Re: Simplify the following:

I see, then let me check the original one and come back.

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