You are Here: Home >< Maths

Unsure on how to answer these questions (binomial expansion c4)

Announcements Posted on
Why bother with a post grad course - waste of time? 17-10-2016

1. The questions in particular are 3 and 6
Im not sure how you solve these as normally
The expansion isn't multiplied by another value . I had thought i needed to multiply first or multiply the end result by whats before it however im not getting any right answers.

How exactly do you solve these questions
To note I can do something like
First few terms of 7x+12/(x+3)(x+4) or (1+x/4)^1/2
But not
(x+1)(1+x/4)^1/2
What exactly do you need to do ?
2. Expand and then multiply.
3. (Original post by Vanetti)

The questions in particular are 3 and 6
Im not sure how you solve these as normally
The expansion isn't multiplied by another value . I had thought i needed to multiply first or multiply the end result by whats before it however im not getting any right answers.

How exactly do you solve these questions
To note I can do something like
First few terms of 7x+12/(x+3)(x+4) or (1+x/4)^1/2
But not
(x+1)(1+x/4)^1/2
What exactly do you need to do ?
Have you got any working out to show? Because I would work out the binomial expansion then multiply by (1+x) for question 3 but you said that you dont get the correct answer?

Posted from TSR Mobile
4. (Original post by Vanetti)

The questions in particular are 3 and 6
Im not sure how you solve these as normally
The expansion isn't multiplied by another value . I had thought i needed to multiply first or multiply the end result by whats before it however im not getting any right answers.

How exactly do you solve these questions
To note I can do something like
First few terms of 7x+12/(x+3)(x+4) or (1+x/4)^1/2
But not
(x+1)(1+x/4)^1/2
What exactly do you need to do ?
(x+1)(1+x/4)^1/2 = (x+1)(1 + x/8 - x^2/128 + x^3/1024 - ...) using the binomial expansion,
and now multiply out as x + x^2/8 - x^3/128 + x^4/1024 - ... + 1 + x/8 - x^2/128 + x^3/1024 - ...
= 1 + 9x/8 + 15x^2/128 - 7x^3/1024 + ...
5. (Original post by HFancy1997)
Have you got any working out to show? Because I would work out the binomial expansion then multiply by (1+x) for question 3 but you said that you dont get the correct answer?

Posted from TSR Mobile
Turns out I did have the correct answer but had an extra
-4x^4 which I didn't realize the question had said in ascending powers of x (so that value isn't needed) thanks for the help I had thought I needed some random method or something

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: August 29, 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
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read here first

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants