Turn on thread page Beta
 You are Here: Home >< Maths

# Binomial Problems question watch

1. Hi again,

any help with this much appreciated!

Expand (1-2x)^-1 as far as the term containing x^3.

I think that is right, its the next part I'm unsure of:

State the values of x for which the expansion is valid

I've got x =/= 0.5, because 2*0.5 = 1 and (1-1) would be zero. Is that what the question means?
2. |2x| < 1
Therefore |x| < 1/2
3. (Original post by Ben121)
|2x| < 1
Therefore |x| < 1/2
Thanks, could you explain a bit more how to get to that please?
4. For an expansion if n is not a positive integer the expansion is only valid for |b/a| < 1. I cannot remember why but I'm sure someone will post.

Turn on thread page Beta
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: March 14, 2011
Today on TSR

### Don't know what to study?

These A-levels give you the most options

### University open days

• University of East Anglia
UEA Mini Open Day Undergraduate
Fri, 4 Jan '19
• University of Lincoln
Mini Open Day at the Brayford Campus Undergraduate
Mon, 7 Jan '19
• Bournemouth University
Wed, 9 Jan '19
Poll
Useful resources

## Make your revision easier

### 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

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups

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