You are Here: Home >< Maths

# Removing logs from both sides Watch

1. Page 7 question 8 last part

How do you remove the logbase10 from both sides?
2. You're missing an attachment. =S
3. (Original post by BananaPie)
You're missing an attachment. =S
http://www.ocr.org.uk/Images/59336-m...me-january.pdf
4. you just do :/ they are the same on both sides so you can just cancel?
5. Divide both sides by log10. The x^2-10/9 could be in brackets, to make it easier to see.
6. Logbase10 ((x^2-10)/x) = logbase10 (9)

Since they're both logbase10 with no other constants or variables added to the equated equation, (x^2-10)/x has to equal 9 in order for this equated equation to work. Hence when you solve it you do not need to bother with Logbase10.

If you're given a situation where logbase10 (2a) = logbase10 (5), then 2a = 5. However if logbase10 (2a) = logbase10 (5) + 3, then you cannot say that 2a = 5. You'll have to convert 3 into a logarithm with base 10.
7. (Original post by Acruzen)
you just do :/ they are the same on both sides so you can just cancel?

(Original post by Konflict)
Divide both sides by log10. The x^2-10/9 could be in brackets, to make it easier to see.
But log 10 / log 10 = syntax error and not 1 ?
8. (Original post by Konflict)
Divide both sides by log10. The x^2-10/9 could be in brackets, to make it easier to see.
Really no.

The inverse operation of taking logs to base 10 is to exponentiate to base 10.
9. (Original post by BananaPie)
Logbase10 ((x^2-10)/x) = logbase10 (9)

Since they're both logbase10 with no other constants or variables added to the equated equation, (x^2-10)/x has to equal 9 in order for this equated equation to work. Hence when you solve it you do not need to bother with Logbase10.
Yes thanks I remember my teacher telling me this
10. (Original post by IShouldBeRevising_)
But log 10 / log 10 = syntax error and not 1 ?
log 10 / log 10 = 1

but that is irrelevant here as that is not the required approach.
11. (Original post by IShouldBeRevising_)
But log 10 / log 10 = syntax error and not 1 ?
Sorry, look at BananaPie's post!
It uses log property: logb(b)^x=x (I think, Mr M will correct me! )
So, log10(10^9)=x^2-10/x
log10(10^9)=9
9=x^2-10/x

I don't know why I said what I said. Just ignore me.
12. (Original post by Mr M)
log 10 / log 10 = 1

but that is irrelevant here as that is not the required approach.
Yes thank you, I understand now.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 4, 2013
Today on TSR

### Does race play a role in Oxbridge admissions?

Or does it play no part?

### The worst opinion about food you'll ever hear

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.