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#1 2013-07-23 01:02:49

EbenezerSon
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Find the truth set of the following.

I have solved the following, but it seems impossible to factorise at some point:

3^2x+1 - 3^x+2 - 3^x+1 = 0.

The book says, x=-1 or -2
It was impossible for to factorise at some point, let alone getting the answer.

I need assistance.

Thanks.

#2 2013-07-23 01:09:20

bob bundy
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Re: Find the truth set of the following.

please make the expression clear with brackets

eg 3^(2x+1)   0r 3^(2x)  + 1

thanks

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

#3 2013-07-23 01:39:13

EbenezerSon
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Re: Find the truth set of the following.

There is no bracket involved in it from where I copied.
It is treated under indices.
I have solved similar problem but this seems insoluble at some point.
I will solvd for you to see where I got stuck.

#4 2013-07-23 02:02:28

EbenezerSon
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Re: Find the truth set of the following.

Here I go.

(3^x)^2 * 3 - 3^x*3^2 - 3^x*3 +1=0

Let 3^x = M. therefore substitution.
3m^2 - 9m - 3m + 1

= 3m^2 - 12m + 1=0
factorization seem impossible here.

#5 2013-07-23 02:15:17

bob bundy
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Re: Find the truth set of the following.

I just wanted to be clear that the problem is:

If so then x = -1 and -2 are not solutions:

This is not zero.

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

#6 2013-07-23 02:17:12

bobbym

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Re: Find the truth set of the following.

Hi;

That can not be factored. You need as Bob suggests to clean the question up.

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 2013-07-23 02:54:57

EbenezerSon
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Re: Find the truth set of the following.

I have solved a similar question successfuly, see.

3^2x+3 - 4(3^x+1) + 1=0

Last edited by EbenezerSon (2013-07-23 05:30:52)

#8 2013-07-23 03:00:04

bobbym

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Re: Find the truth set of the following.

Hi;

Please bracket that a little better.

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 2013-07-23 03:21:06

EbenezerSon
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Re: Find the truth set of the following.

That is how it exist in the book I am working with.

#10 2013-07-23 03:22:38

bobbym

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Re: Find the truth set of the following.

What does 3^2x+3 mean?

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.

#11 2013-07-23 03:31:15

bob bundy
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Re: Find the truth set of the following.

I think it is unlikely that a book would use the symbol ^

please look again at post 5

Is the equation I have put there the one in your book?

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

#12 2013-07-23 04:37:09

EbenezerSon
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Re: Find the truth set of the following.

bobbym wrote:

What does 3^2x+3 mean?

It means the 3 has raised to the power 2x+3.

#13 2013-07-23 04:44:58

bobbym

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Re: Find the truth set of the following.

Hasn't he raised a good point with

bob bundy wrote:

I think it is unlikely that a book would use the symbol ^

I would agree, but you say it is there! But then his post #5 is correct and that is not a solution.

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.

#14 2013-07-23 04:51:24

EbenezerSon
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Re: Find the truth set of the following.

bobbym wrote:

Hasn't he raised a good point with

bob bundy wrote:

I think it is unlikely that a book would use the symbol ^

I would agree, but you say it is there! But then his post #5 is correct and that is not a solution.

The book did not use the symbol ^, I rather used it , because the 2x +3 is at the top of the 3 in the book.

#15 2013-07-23 04:58:21

bobbym

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Re: Find the truth set of the following.

Hi;

This is exactly what is in the book then?

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.

#16 2013-07-23 05:00:19

EbenezerSon
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Re: Find the truth set of the following.

bob bundy wrote:

I just wanted to be clear that the problem is:

If so then x = -1 and -2 are not solutions:

This is not zero.

Bob

Yes that's how it is arranged, in the book.

Last edited by EbenezerSon (2013-07-23 05:03:09)

#17 2013-07-23 05:01:28

EbenezerSon
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Re: Find the truth set of the following.

bobbym wrote:

Hi;

This is exactly what is in the book then?

Yes Sir!. Positive 1 is at the end

Last edited by EbenezerSon (2013-07-23 05:03:46)

#18 2013-07-23 05:04:42

bobbym

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Re: Find the truth set of the following.

It is obviously some sort of typo.

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.

#19 2013-07-23 05:09:34

EbenezerSon
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Re: Find the truth set of the following.

bobbym wrote:

It is obviously some sort of typo.

The book is before me now and has positive 1 just at the end.

Last edited by EbenezerSon (2013-07-23 06:25:55)

#20 2013-07-23 05:35:04

bobbym

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Re: Find the truth set of the following.

It still looks like a mistake in the book. -1 and -2 are not roots of that equation.

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.

EbenezerSon
Full Member

Offline

#22 2013-07-23 05:53:41

bobbym

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Re: Find the truth set of the following.

I could not solve that by hand. It takes a computer to solve it. The answer involves complex numbers further showing that the problem is mistyped.

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.

#23 2013-07-23 06:53:08

EbenezerSon
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Re: Find the truth set of the following.

Yeb I must believe you, c'os the author stated explicitly that, a student should forgive any mistake that would be found in the book. Is just at the beginning of  the book .
:-) But still you're darling!

Last edited by EbenezerSon (2013-07-23 06:53:35)

#24 2013-07-23 06:55:23

bobbym

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Re: Find the truth set of the following.

If you are marked wrong about it then you will have the consolation of knowing that I would have been marked wrong too.

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.

#25 2013-07-23 07:50:40

bob bundy
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Re: Find the truth set of the following.

So now the question has become:

x = -1

x = -2

Closest equation with those answers that I can find:

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei