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**BenLee****Guest**

Hello I have been trying this questions forever to no avail. Could anyone help me?

A. Using the laws of logarithms, simplify x-0.45 = 0.521 and evaluate for x [5 marks]

B. Find the fifth root of 600 using logarithms. [4 marks]

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

Hi;

A. Using the laws of logarithms, simplify x-0.45 = 0.521 and evaluate for x [5 marks]

Why do you need logarithms to solve a linear equation?

Add .45 to both sides.

For B, what are you allowed to use? A calculator? A log table?

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**Benlee****Guest**

Wow... Didn't know it was that simple... haha, but it is an assignment and unfortunately I need to use logarithm for it. I was thinking of putting "lg" on both sides, but not sure if that's the correct way.

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

Do you have the right problem?

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**BenLee****Guest**

Apologies, knew something was not right. I typed wrongly.

A. Using the laws of logarithms, simplify** x^-0.45** = 0.521 and evaluate for x [5 marks]

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

x^-0.45 = 0.521

When you take the log of both sides what do you get?

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**BenLee****Guest**

lg x^-0.45 = lg 0.521

Is this right? Seems weird to me.

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

That is correct and what is log(x^(-.45)) ?

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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**BenLee****Guest**

I got -0.45 lgx = lg 0.521

lg x = 0.629

Is that the answer or do i need to move the lg to make x the subject? o.o

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

What did you get for lg 0.521?

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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**BenLee****Guest**

I got -0.283162276 and i divided that by -0.45 to get 0.629

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

That is correct. So what do you have left?

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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**BenLee****Guest**

I have lg x = 0.629 left.

Should i make x the subject now or is that the answer? o.o

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

What is the inverse of log(x)?

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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**BenLee****Guest**

Is it log x^-1?

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

You are using the common log?

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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**BenLee****Guest**

I guess so, the other log thingy is "ln"

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,466

When we say log(3) we mean what power must 10 be raised to, to get 3.

So what do you think now is the inverse of log? You should get raising 10 to the power of.

So taking 10^ of both sides what do you get?

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

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