You are Here: Home >< Maths

C3 differentiation help Watch

Announcements
1. Hi,

There's a few differentiation questions that I'm stuck on.

f (x)= (-4x)/((1+x^2)^2)
I started doing it by using the quotient rule but I can't get to the answer at the back of the book.

f (x) = x ((9-2x^2)^1/2)
The first part of the question was to work out f'(x) of (9-2x^2)^1/2 which I did using chain rule.
The next part of the question's to work out f'(x) of the whole function which I tried to do using the product rule but I keep getting it wrong.

I also had a problem with differentiating (2x-1)^3 (x+1)^3 as I wasn't sure which rule/rules to use in which order.

Any help on any of the questions would be really appreciated
2. (Original post by VioletPhillippo)
Hi,

There's a few differentiation questions that I'm stuck on.

f (x)= (-4x)/((1+x^2)^2)
I started doing it by using the quotient rule but I can't get to the answer at the back of the book.

f (x) = x ((9-2x^2)^1/2)
The first part of the question was to work out f'(x) of (9-2x^2)^1/2 which I did using chain rule.
The next part of the question's to work out f'(x) of the whole function which I tried to do using the product rule but I keep getting it wrong.

I also had a problem with differentiating (2x-1)^3 (x+1)^3 as I wasn't sure which rule/rules to use in which order.

Any help on any of the questions would be really appreciated
Well firstly, it's hard to help when nobody knows where exactly you went wrong because you seems to have solid methods.

Secondly, I'd ignore the product rule on that last one because

then just chain rule it.
3. (Original post by RDKGames)
Well firstly, it's hard to help when nobody knows where exactly you went wrong because you seems to have solid methods.

Secondly, I'd ignore the product rule on that last one because

then just chain rule it.
Thanks, I've done the last question correctly now . For the 1st question using the quotient rule I got as far as subbing in the values (1+x^2)^2 (-4x) - (-4)(4x+4x^3) /(1+x^2)^4 but I'm struggling with the simplifying without expanding it out.

Question 2, using the product rule I subbed in x (-2x/((9-2x^2)^1/2) + 1 ((9-2x^2)^1/2) but again I'm struggling with the simplifying.

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: October 11, 2016
Today on TSR

Oxbridge

Even more elitist than everyone thought?

Physically ill after being cheated on

Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• 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

Chat with other maths applicants

Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• 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

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}