Find all School-related info fast with the new School-Specific MBA Forum

It is currently 24 Oct 2014, 22:25

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
CEO
CEO
User avatar
Joined: 21 Jan 2007
Posts: 2769
Location: New York City
Followers: 8

Kudos [?]: 257 [0], given: 4

If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 16 Nov 2007, 07:16
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

86% (02:05) correct 14% (00:36) wrong based on 19 sessions
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)
[Reveal] Spoiler: OA

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.
SVP
SVP
User avatar
Joined: 07 Nov 2007
Posts: 1829
Location: New York
Followers: 27

Kudos [?]: 472 [0], given: 5

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 16 Nov 2007, 07:21
bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
What is f(1/x) in terms of f(x)?

f[x]
-f[x]
1/f[x]
-1/f[x]
2*f[x]


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?
Director
Director
User avatar
Joined: 30 Nov 2006
Posts: 592
Location: Kuwait
Followers: 11

Kudos [?]: 154 [0], given: 0

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 16 Nov 2007, 11:57
f(x) = x^2 / (x^4 - 1)
What is f(1/x) in terms of f(x)?

f[x]
-f[x]
1/f[x]
-1/f[x]
2*f[x]

f(1/x) = (1/x)^2 / [(1/x)^4 - 1]
= 1/x^2 / [1/x^4 - 1]

Clearly, the only answer that could make sense is C


what is the OA ?
Intern
Intern
avatar
Joined: 12 Feb 2007
Posts: 14
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 16 Nov 2007, 12:14
It is B f(x) = x^2/(X^4 - 1)
f(1/x) = (1/x)^2/((1/x)^4 -1)
= (1/x)^2/(-(x^4- 1)/x^4)
= x^4/x^2 * -(1- x^4)
= (x^2 * x^2)/ x^2 * -(1-x^4)
= f(x) * (x2/ -x2)
= -f(x)
Director
Director
avatar
Joined: 09 Aug 2006
Posts: 767
Followers: 1

Kudos [?]: 52 [0], given: 0

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 17 Nov 2007, 00:55
bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
What is f(1/x) in terms of f(x)?

f[x]
-f[x]
1/f[x]
-1/f[x]
2*f[x]


If x = 2 then f(x) = 4/15 and f(1/x) = -4/15 which is equal to -f(x)

answer B.
CEO
CEO
User avatar
Joined: 29 Mar 2007
Posts: 2593
Followers: 16

Kudos [?]: 198 [0], given: 0

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 17 Nov 2007, 22:49
bmwhype2 wrote:
f(x) = x^2 / (x^4 - 1)
What is f(1/x) in terms of f(x)?

f[x]
-f[x]
1/f[x]
-1/f[x]
2*f[x]


(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.
VP
VP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1088
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 6

Kudos [?]: 308 [0], given: 170

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 25 Sep 2014, 21:58
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
_________________

Kindly press "+1 Kudos" to appreciate :)

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23409
Followers: 3613

Kudos [?]: 28932 [0], given: 2871

Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)? [#permalink] New post 25 Sep 2014, 22:37
Expert's post
Re: If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?   [#permalink] 25 Sep 2014, 22:37
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic If f(x) = (x^4 - 1)/(x^2), what is f(1/x) in terms of f(x)? bmwhype2 3 19 Nov 2007, 09:02
Experts publish their posts in the topic If f(x) = x/(x + 1), what is f(1/x) in terms of x ? bmwhype2 6 12 Nov 2007, 13:44
For which of the following functions f is f(x) = f(1-x) for Matador 1 06 Apr 2006, 14:17
For which of the following functions is f(x) = f(1-x) for mophead 6 01 Sep 2005, 05:14
For which of the following functions f is f(x) = f(1 - x) Folaa3 6 21 Aug 2005, 18:27
Display posts from previous: Sort by

If f(x) = x^2/(x^4 - 1), what is f(1/x) in terms of f(x)?

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.