Math Is Fun Forum

timberwo7ves

Member

Registered: 2007-08-24

Posts: 4

c3 inverse functions :s

hmm trying to find the inverse function of f(x), where x is used twice, never done before :s

trying to find

if you have the Heinemann C3 book, it's page 27, mixed exercise 2F, q7

I've tried splitting into two parts, i.e. the numerator inverted would be

and the denominator would be

, but I'm not sure where to go from there, if that's even the right steps to take in the first place :s

=]]

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: c3 inverse functions :s

This is basically the same as trying to make x the subject of the equation. In this case, the numerator has the same order as the denominator, so you would do that by first removing a constant term.

From there you can get the inverse function by switching back again.

---

Why did the vector cross the road?
It wanted to be normal.

timberwo7ves

Member

Registered: 2007-08-24

Posts: 4

Re: c3 inverse functions :s

ty I get that, but (and here is where I might confuse myself a bit more) is that method (from the last two lines of your post) the same as saying that:

if yes, then cool, if no, then.. err.. :s

Last edited by timberwo7ves (2007-08-24 04:06:12)

timberwo7ves

Member

Registered: 2007-08-24

Posts: 4

Re: c3 inverse functions :s

or even, new question, same concept, which should hopefully clear up both.

find

trying to make x the subject of the formula:

therefore,

but the answer in the back of the book is:

sorry about the double post, didn't want to clutter that last bit up :s

Last edited by timberwo7ves (2007-08-24 04:45:52)

reddog

Member

Registered: 2007-07-23

Posts: 7

Re: c3 inverse functions :s

or even, new question, same concept, which should hopefully clear up both.

find

trying to make x the subject of the formula:

It's wrong!

If

then

So, start from

anf solve for x.
In this case:

Then

Last edited by reddog (2007-08-24 05:35:33)

timberwo7ves

Member

Registered: 2007-08-24

Posts: 4

Re: c3 inverse functions :s

thanks, I get it more.. but I can't see how you've gone from

sorry, can you show that rearrangement :s

Last edited by timberwo7ves (2007-08-24 06:06:08)

reddog

Member

Registered: 2007-07-23

Posts: 7

Re: c3 inverse functions :s

timberwo7ves

Member

Registered: 2007-08-24

Posts: 4

Re: c3 inverse functions :s

well when you put it like thaaat!

I feel slightly retarded... thanks for your help guys =]]]]

Last edited by timberwo7ves (2007-08-24 08:05:04)