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#151 2013-07-24 21:50:40

EbenezerSon
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Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

I don't seem to understand the step 3.

I thought, it would be something like:
xlog10 - log2 + xlog3 = 0

I claim the above because of the following:

2 - 2log5 = log10^2 - log5^2 = log4.

Why didnt it take xlog10. because 2 is the log and not the base. I think it cant be xlog2.


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#152 2013-07-24 21:53:15

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

Hi;

This step?


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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#153 2013-07-24 22:04:51

EbenezerSon
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Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

Yes. if you look at the my example, log ten raises to the power two. And not log5^2


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#154 2013-07-24 22:09:50

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

log(3^x) breaks down into xlog(3) regarldless of base 10 or base e or base 2.

Same for log(2^(x-1)) = (x-1) log(2). According to the rule

log(a^b) = b * log(a)


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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#155 2013-07-24 22:26:59

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

Yes, I understand that law, so now, log2^x-1= xlog2 - log2

So does my example mean, 2 - 2log5 = log5^2-2.

If so why is it equall to log10^2 - log5^2. and not log5^2 - log5^2 in order to go according to the law.


I know only one thing - that is that I know nothing

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#156 2013-07-24 22:29:12

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

What example do you mean?


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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#157 2013-07-24 22:55:13

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

The book has this example.
2 - 2log5 = log10 - log5^2 =log4

why should not it be, 2 - 2log5 = "log5^2" -log5^2 so that it will go by the law.

With example it has log10^2, I think should be log5^2


I know only one thing - that is that I know nothing

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#158 2013-07-24 22:57:25

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

Hi;

You are done with the old problem and wish to do another one?


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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#159 2013-07-24 23:14:59

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

I am comparing two things because I dont understand your step 2.
The is an example from the book:  2-2log5 = log10^2 - log5^2 = log4
so does 2-2log5 mean log5^2-2?

That what I want to know.


I know only one thing - that is that I know nothing

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#160 2013-07-24 23:19:53

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

2 - 2 log(5) is the same as 2 - log(5^2)  you can not switch them.


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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#161 2013-07-25 00:16:17

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

How different is this x-1log2 in the previous problem from 2-2log5 in the example.

Because I see it that one must apply the same method, but the method used to solve both are different.
Please see this;
x-1 log2 = xlog2-1log2.
(The same base used).

And

2-2log5 = log10^2-log5^2.
(Different bases used).
why is it log10^2 and not log5^2 instead. So that the whole thing  would be;

log5^2-log5^2,

Please, explain to me why.

Last edited by EbenezerSon (2013-07-25 00:33:48)


I know only one thing - that is that I know nothing

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#162 2013-07-25 00:33:26

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

2-2log5 = log10^2-log5^2

Where are you getting that 10 from?


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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#163 2013-07-25 00:41:33

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

Thats what is written in the book.
It used log ten for the unknown log of the two. Hence

2-2log5=log10^2-log5^2

But I dont know why.

Is that wrong if so how should it be?


I know only one thing - that is that I know nothing

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#164 2013-07-25 00:45:10

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

No, that is correct. I did not see it at first.


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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#165 2013-07-25 00:59:17

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

Please I what you to answer my question at #161


I know only one thing - that is that I know nothing

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#166 2013-07-25 01:02:51

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

(x-1) log2 = xlog2-1log2.

That has nothing to do with bases of exponents. It uses another law of algebra called the distributive property:

a(b + c) = ab + ac or (b + c)a = ab + ac


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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#167 2013-07-25 01:15:07

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

Please provide a link for that.
Is not among the law of log in my book.

And why log10^2 in # 163 correct?


I know only one thing - that is that I know nothing

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#168 2013-07-25 01:17:39

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

log(10^2) is 2 log(10). log(10) in base 10 is 1.

http://www.mathsisfun.com/definitions/d … e-law.html


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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#169 2013-07-25 03:58:41

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

bobbym wrote:

Okay, I will provide the steps:

Take the log of both sides.

Why the last step is not:

Since the law says. for instance log2-log2 = log2/log2.


I know only one thing - that is that I know nothing

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#170 2013-07-25 15:21:48

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

What law says 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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#171 2013-07-25 19:32:59

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

This is what I mean, and it is one of the laws of logarithm in my book:

logx - logy = log(x/y).
This is what I mean, and I see you did not apply it at that step. Why didn't you?


I know only one thing - that is that I know nothing

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#172 2013-07-25 20:03:09

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

That is not the law:

log2-log2 = log2/log2.

Take a close look at that,
log2-log2  = 0
log2/log2. = 1

0 ≠ 1


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

#173 2013-07-26 05:32:47

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

bobbym wrote:

Okay, I will provide the steps:

Take the log of both sides.

Add log(2) to both sides.


.

Then how did you arrived at the last stage? Could you explain to me?

Why did you added log two to both sides?

Thanks

Last edited by EbenezerSon (2013-07-26 05:34:29)


I know only one thing - that is that I know nothing

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#174 2013-07-26 12:46:46

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 88,528

Re: Simplify the following:

If you were solving

x - 2 = 0

you would add 2 to both sides

x -2 + 2 = 2

-2 + 2 = 0

x = 2.

Notice how x is all by itself on the left side.

I am doing the same thing in that equation. Trying to get x all by itself on the left.


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

#175 2013-07-27 03:54:01

EbenezerSon
Member
Registered: 2013-07-04
Posts: 466

Re: Simplify the following:

But I am sure if you had not added log2 to both sides you would still arrive at the same answer, is not that?

------------------
xlog2 - "log2" +xlog3 =0. From this stage you took off the "log2", why that happened.


I know only one thing - that is that I know nothing

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