You are Here: Home >< Maths

Can someone tell how to find this general rule watch

1. For a given equation
, to find x , it says use , and then .

My question is how do I find this underlined part , ??( the book does not mention it)
2. Solve
u-v=d
and
uv=(c/3)^3
simultaneously.

(For a given equation you will know c and d.)
3. (Original post by rnd)
Solve
u-v=d
and
uv=(c/3)^3
simultaneously.

(For a given equation you will know c and d.)
My question is how do I deirive [ u-v=d , and uv = (c/3)^3,}.

given only that
soory if my question isnt specific
4. Are you sure you want to derive those equations?

If you just want to solve them then you have u=d+v, sub that in uv=(c/3)^3 rarrange to get a quadratic equation and solve it to get v in terms of c and d.

But how can you not be using a?
5. yes, I want to know how they found the equations(I think the bok assumes its obvious .I know how to find x using u and v.
6. (Original post by rbnphlp)
yes, I want to know how they found the equations(I think the bok assumes its obvious .I know how to find x using u and v.
OK. I'm giving up on this one then. Hope someone else helps you out.

My point about a still stands though. How can x depend on c and d but not a? It can't. What's the book by the way?
7. It looks like the standard cubic solution equation in the special case where b=0 and a=1. There's a derivation of the solution on this page:

http://en.wikipedia.org/wiki/Cubic_e...cubic_function
8. (Original post by rnd)
OK. I'm giving up on this one then. Hope someone else helps you out.

My point about a still stands though. How can x depend on c and d but not a? It can't. What's the book by the way?
History of mathematics quite intresting

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: July 15, 2009
Today on TSR

Edexcel C4 Maths Unofficial Markscheme

Find out how you've done here

1,779

students online now

Exam discussions

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

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