You are Here: Home >< A-levels

# C2 Logs... I hate them and need help

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. (log3(81)+log3(243))/(log3(x)) = log3(x)

Need urgent help with this one.After simplifying the numerator, do I multiply both sides by log3(x) ?
2. (Original post by kieton123)
(log3(81)+log3(243))/(log3(x)) = log3(x)

Need urgent help with this one.After simplifying the numerator, do I multiply both sides by log3(x) ?
check my solution
3. (Original post by kieton123)
(log3(81)+log3(243))/(log3(x)) = log3(x)

Need urgent help with this one.After simplifying the numerator, do I multiply both sides by log3(x) ?
Yes multiply both sides by log3x

you should end up with log3x squared =9

now square root both sides

log3x= +- 3

solve from there
4. (Original post by kieton123)
(log3(81)+log3(243))/(log3(x)) = log3(x)

Need urgent help with this one.After simplifying the numerator, do I multiply both sides by log3(x) ?
3^4 = 81 and 3^5 = 243

let log3(x) be y and make a quadratic equation by multiplying everything by y
i got x as 243 and 1/3.
5. (Original post by RizK)
3^4 = 81 and 3^5 = 243

let log3(x) be y and make a quadratic equation by multiplying everything by y
i got x as 243 and 1/3.
Apparently x is 27, Imran got the answer
6. (Original post by kieton123)
Apparently x is 27, Imran got the answer
I just checked and this is the way they have done it in the C2 book... mind telling me where you got the question from? thanks
7. (Original post by RizK)
3^4 = 81 and 3^5 = 243

let log3(x) be y and make a quadratic equation by multiplying everything by y
i got x as 243 and 1/3.

8. If , then

You can verify your answer by plugging x back into the original equation and seeing if both sides output the same value.
9. (Original post by RizK)
I just checked and this is the way they have done it in the C2 book... mind telling me where you got the question from? thanks
Ok man, its the "Revise Edexcel AS Mathematics AS Workbook"
10. Og my god i read the question wrong xD I thought log3(81)was a serparate terrm lol
Cheers!
11. (Original post by Reda2)
You're missing a solution >
You must also consider
12. (Original post by edothero)
You're missing a solution >
You must also consider
Just wanted to show him the solution, pretty sure he knows that.

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 20, 2016
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:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets