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Can someone explain please? C3

F(x)=2+ln(3x-2)

Find ff(1)

What does ff mean and how do you do it?


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You evaluate f(1) exactly and then substitute this as x.

f(x) means that when we input x we get f(x) as the output.

ff(1) gives the output when we input f(1) as x in f(x).

Its easy. :smile:

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This is not recognised notation.
Reply 3
Avatar for Gax
Gax
16
You substitute x=1 into that equation there, then you substitute the answer that you get back into the equation and that will be the answer :smile:
Original post by MaheenMaheen
F(x)=2+ln(3x-2)

Find ff(1)

What does ff mean and how do you do it?


Posted from TSR Mobile


This is standard notation and means

It means f of f of x

Put 1 in and find f(1)

Then you use that answer to fin f[f(1)]


NB you need to take care as you used F(x) originally - for functions use lower case throughout
(edited 9 years ago)
some books write this as f2(1).... i think ff(1) is less confusing ff(sake)
Thanks a lot guys!


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Avatar for Zen-Ali
Zen-Ali
8
Original post by the bear
some books write this as f2(1).... i think ff(1) is less confusing ff(sake)


Lmao.
Original post by Old_Simon
This is not recognised notation.


Are you talking about "ff(x)"? If so, this notation appears in A-Level Maths papers.
Original post by ThatPerson
Are you talking about "ff(x)"? If so, this notation appears in A-Level Maths papers.

Is it in the spec ?
Original post by Old_Simon
Is it in the spec ?


Sort of - notation like ff−1(x)ff^{-1}(x) is mentioned in the spec.

For the type of question in the OP, see the original C3 June 2013 paper, where one part asks candidates to "determine the exact value of ff(0)".
Original post by ThatPerson
Sort of - notation like ff−1(x)ff^{-1}(x) is mentioned in the spec.

For the type of question in the OP, see the original C3 June 2013 paper, where one part asks candidates to "determine the exact value of ff(0)".

I don't dispute it was in an exam. I ask if it is in the supplied notation specification.
Original post by Old_Simon
Is it in the spec ?


gf is

so, yes


NB I only checked the Edexcel spec
Original post by Old_Simon
I don't dispute it was in an exam. I ask if it is in the supplied notation specification.


I haven't checked the Edexcel spec, but surely if it was in an Edexcel exam it implies that it is included in the specification and candidates are expected to understand it?
Original post by Old_Simon
Is it in the spec ?


This may help with your other confusion

If the students "understands" what composite functions are then they can apply the understanding to this question

When all they do is practice a set of questions - they may not have seen this example
Original post by ThatPerson
I haven't checked the Edexcel spec, but surely if it was in an Edexcel exam it implies that it is included in the specification and candidates are expected to understand it?

I don't mean to be pedantic. But recognised - hence useable - notation for each exam board is published in a document which is freely available for download. There is no excuse for any student not to have a copy of that document and be familiar with it's content. Unless they are relying on their teacher to tell them everything they need to know.
Original post by TenOfThem
gf is

so, yes


NB I only checked the Edexcel spec


F^2(x) can also mean second derivative of f(x), couldnt it? Or have we to put the brackets for that? :smile:

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Original post by RoyalBlue7
F^2(x) can also mean second derivative of f(x), couldnt it? Or have we to put the brackets for that? :smile:

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I would not use f2(x)f^2(x) for either ff(x) nor f"(x)
Original post by TenOfThem
I would not use f2(x)f^2(x) for either ff(x) nor f"(x)


So how do you symbolize the 100th derivative of a function?

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Original post by RoyalBlue7
So how do you symbolize the 100th derivative of a function?

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f'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''(x)

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