You are Here: Home >< Maths

# Need help with this series approximation. watch

1. Fill in the values for p,q and r in this series approximation. Use decimals, or a fraction with integers top and bottom, so 0.75 OR 3/4.

(a^3)/(a^2-x^2)^1.5 = p +q(x^2/a^2) + r(x^2/a^2)^2
2. (Original post by sidhi12)
Fill in the values for p,q and r in this series approximation. Use decimals, or a fraction with integers top and bottom, so 0.75 OR 3/4.

(a^3)/(a^2-x^2)^1.5 = p +q(x^2/a^2) + r(x^2/a^2)^2
I presume you're comfortable with the expansion of (1+x)^n, where the constant term is "1".

Here you have a^2. So, you need to extract a factor first of all to get it into the desired from (1+ ...).
3. (Original post by ghostwalker)
I presume you're comfortable with the expansion of (1+x)^n, where the constant term is "1".

Here you have a^2. So, you need to extract a factor first of all to get it into the desired from (1+ ...).
I've done up to there and got the expansion. However when I divide the a^3 by the expansion, I don't end up with an expression like the one with the p,q and r
4. (Original post by sidhi12)
I've done up to there and got the expansion. However when I divide the a^3 by the expansion, I don't end up with an expression like the one with the p,q and r
You shouldn't need to divide by the expansion.

(a^3)/(a^2-x^2)^1.5 = (a^3)(a^2-x^2)^-1.5

and your expansion is in the numerator.
5. Thanks

### Related university courses

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: November 10, 2017
Today on TSR

### Top unis in Clearing

Tons of places at all these high-ranking unis

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