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If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
A. f(x)
B. -f(x)
C. 1/f(x)
D. -1/f(x)
E. 2*f(x)
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Originally posted by
bmwhype2 on 16 Nov 2007, 07:16.
Last edited by
Bunuel on 25 Sep 2014, 22:43, edited 2 times in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
If x = 2 then f(x) = 4/15 and f(1/x) = -4/15 which is equal to -f(x)
answer B.
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
f(1/x) = (1/x)^2 / ((1/x)^4 - 1) = x^4/((x^2)* (1- x^4))
= x^2/(1-x^4)= - ( x^2/(x^4-1))
= -f(x)
I pick B.
What is OA?
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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f(x) = x^2 / (x^4 - 1)
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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It is B f(x) = x^2/(X^4 - 1)
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
(1/x^2)/(1/x^4-1) --> (1/x^2)/(1-x^4)/(x^4) --> just cancel out the x's. we get x^2/(1-x^4) --> x^2/-(x^4-1) ---> -(x^2)/(x^4-1)
so we get -f(x). So B
U can do it algebraically, which i suggest u do first, but if its not workin out for ya then just plug in a value for x. (obviously use easy numbers).
Just make X=2.
4/16-1 ---> 4/15
Then (1/4)/(1/16-1) ---> 1/4/-15/16 --> -4/15 ---> so its b b/c -(-4/15) ---> 4/15.
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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\(f(x) = \frac{x^2}{x^4 - 1}\)
\(\frac{1}{f(x)} = \frac{x^4 - 1}{x^2} = x^2 - \frac{1}{x^2}\)
\(\frac{1}{f(\frac{1}{x})} = \frac{1}{x^2} - x^2 = \frac{-1}{f(x)}\)
\(f(\frac{1}{x}) = -f(x)\)
Answer = B
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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GK_Gmat wrote:
bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
If x = 2 then f(x) = 4/15 and f(1/x) = -4/15 which is equal to -f(x)
answer B.
how , f(1/x) = -4/15
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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Can someone explain the answer to this question with the number picking technique?
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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Hi eddyki,
You can absolutely TEST VALUES on this question. Here's how:
We're given a function to work with: f(X) = (X^2)/(X^4 -1)
We're asked to consider how the f(X) and the f(1/X) relate to one another, so we have to calculate both options.
TESTING X = 2 gives us...
f(2) = (4)/(16 - 1) = 4/15
f(1/2) = [(1/2)^2]/[(1/2)^4 - 1]
= [1/4]/[1/16 - 1]
= [1/4]/[-15/16]
= [1/4][-16/15]
= -4/15
So after doing all of these little calculations, we have proof that f(X) and the f(1/X) give OPPOSITE results.
This means that f(1/X) is the NEGATIVE of f(X).
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If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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\(f(x) = x^2/(x^4-1)\) that means that\(f(1/x) = (x^4-1)/x^2\)
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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I find easiest way just plug in x=2, then you get f(x) = 4/15 and f(1/x) = -4/15, thus answer is B
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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f(1/x)= (1/x ^ 2)/((1/x) ^4 -1)
= (1/x ^ 2)/((1-x^4)/x^2)
= x^2/ (1 -x^4)
= - x^2/ (x^4 -1 )
=-f(x)
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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My big issue with most of the people solving is they skip basically all the steps. Not really good for learning when you do that. Here is a complete solution and a good video explaining how function notation works.
https://www.youtube.com/watch?v=T6-Zdr5w_bE
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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bmwhype2 wrote:
If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
So let's plug in
x = 2
f(2) = 4/15
f(1/2) = 1/4 * 16/-15 = -4/15
f(x) = -f(x)
B
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Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?
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04 Feb 2019, 21:27
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67% (01:37) correct 
