## Multiple Choice Problem

For the discussion of math. Duh.

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### Multiple Choice Problem

Ok, I know what I did wrong .

SherryYang wrote:f(x) = x^3-x-6

g(x) = inverse of f(x)

Find f'(g(0))g'(0)

-6
-1
0
1
Cube root of 6

I got -11, which is none of the answers.

Please do not edit out your posts after you've asked a question. This is an anti-homework measure ~~Felstaff
Last edited by SherryYang on Wed Nov 30, 2011 8:18 pm UTC, edited 1 time in total.
SherryYang

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### Re: Multiple Choice Problem

What's f(g(x))? What do you get if you apply the chain rule when differentiating that expression?
ameretrifle wrote:Magic space feudalism is therefore a viable idea.

jestingrabbit

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### Re: Multiple Choice Problem

jestingrabbit wrote:What's f(g(x))? What do you get if you apply the chain rule when differentiating that expression?

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

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### Re: Multiple Choice Problem

As a general rule, don't delete your post after your question was answered. Others using the search function might find it useful, in the future. It's something like this comic.
What they (mathematicians) define as interesting depends on their particular field of study; mathematical anaylsts find pain and extreme confusion interesting, whereas geometers are interested in beauty.

z4lis

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### Re: Multiple Choice Problem

Is it just me, or is the function g ill-defined, as long as I assume f: R -> R?
It could be defined as something like f: [-1/sqrt(3),1/sqrt(3)] -> [f(1/sqrt[3]),f(-1/sqrt(3)], but that looks a bit arbitrary.
mfb

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### Re: Multiple Choice Problem

mfb wrote:Is it just me, or is the function g ill-defined, as long as I assume f: R -> R?
It could be defined as something like f: [-1/sqrt(3),1/sqrt(3)] -> [f(1/sqrt[3]),f(-1/sqrt(3)], but that looks a bit arbitrary.

It is globally illdefined, but its well defined around 0, which is where it counts for the question. Its not that arbitrary, just a little.

jestingrabbit wrote:What's f(g(x))? What do you get if you apply the chain rule when differentiating that expression?

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

Yes, yes it is.
ameretrifle wrote:Magic space feudalism is therefore a viable idea.

jestingrabbit

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Location: Sydney

### Re: Multiple Choice Problem

Editing your posts to erase the question after someone asks it isn't polite. It makes the thread useless for anyone else.
One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision - BR

Last edited by JHVH on Fri Oct 23, 4004 BCE 6:17 pm, edited 6 times in total.

Yakk

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### Re: Multiple Choice Problem

If g(x) is the inverse of f(x) then f(g(x))=x by definition
I have discovered a truly marvelous proof of this, which this margin is too narrow to contain.
tomtom2357

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### Re: Multiple Choice Problem

Please don't dig out all the old threads.
You forgot that there is a derivative involved in the question.
mfb

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### Re: Multiple Choice Problem

Wow whose bumping all those old threads !!!
Darrell88

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