You are Here: Home >< Maths

# strange + & - behaviour (Help please!) watch

1. hi,

i was revising some a level maths and i did a question in which my solution came to:

0.5ln (3+/- sqrt8)

now this is correct but the back of the book has:

+/- 0.5ln(3+sqrt8)

i tried playing around with the former but couldn't find a justifiable way of getting it to the second form, but they give the same end result. i.e. basically i don't know how to take out the +/- from before sqrt (8) to outside the expression without doing anything to the 3 at the same time.

P
2. 1/(3 + sqrt 8) = 3 - sqrt 8, right?
3. (Original post by generalebriety)
1/(3 + sqrt 8) = 3 - sqrt 8, right?
its the simplest of things that one misses out - surd manipulation! thanks - i get it now
4. Aye. I thought it was a mistake at first, posted, and then quickly deleted my post to hide the evidence when I realised.

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: August 21, 2007
Today on TSR

### University open days

Wed, 21 Nov '18
• Buckinghamshire New University
Wed, 21 Nov '18
• Heriot-Watt University
Wed, 21 Nov '18
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