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

It is currently 31 Jul 2015, 17:39
GMAT Club Tests

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 x is not equal to zero, and x = sqrt(4xy-4y^2), then in

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Manager
Manager
avatar
Joined: 11 May 2007
Posts: 107
Followers: 1

Kudos [?]: 12 [0], given: 0

If x is not equal to zero, and x = sqrt(4xy-4y^2), then in [#permalink] New post 16 Nov 2007, 11:19
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If x is not equal to zero, and x = sqrt(4xy-4y^2), then in terms of y, x =

(A) 2y
(B) y
(C) y/2
(D) (-4y^2)/1-2y
(E) -2y
Manager
Manager
User avatar
Joined: 01 Oct 2007
Posts: 87
Followers: 0

Kudos [?]: 14 [0], given: 0

Re: Equation [#permalink] New post 16 Nov 2007, 11:29
yogachgolf wrote:
If x is not equal to zero, and x = sqrt(4xy-4y^2), then in terms of y, x =

(A) 2y
(B) y
(C) y/2
(D) (-4y^2)/1-2y
(E) -2y


Square both sides:

x^2 = 4xy - 4y^2

Bring everything to the left:

x^2 - 4xy + 4y^2 = 0

Factor:

(x - 2y)^2 = 0

So x = 2y.
CEO
CEO
User avatar
Joined: 29 Mar 2007
Posts: 2585
Followers: 17

Kudos [?]: 248 [0], given: 0

Re: Equation [#permalink] New post 16 Nov 2007, 23:32
yogachgolf wrote:
If x is not equal to zero, and x = sqrt(4xy-4y^2), then in terms of y, x =

(A) 2y
(B) y
(C) y/2
(D) (-4y^2)/1-2y
(E) -2y


Theres an alternative to straight algebra.

Plug in 2 for y. We eventually get x^2-8x+16=0 (x-4)(x-4)=0

so x=4. Since y =2 2y=4=x.

Now this method isnt full proof as other answer choices may yield the same result. E could be a candidate b/c -2*-2=4. So try -2 in the equation for y. It turns out its not the same.

I only use this when for some reason I can't figure out how to factor something etc.. Id suggest tryin algebra first.
Director
Director
avatar
Joined: 09 Aug 2006
Posts: 763
Followers: 1

Kudos [?]: 81 [0], given: 0

Re: Equation [#permalink] New post 17 Nov 2007, 00:03
yogachgolf wrote:
If x is not equal to zero, and x = sqrt(4xy-4y^2), then in terms of y, x =

(A) 2y
(B) y
(C) y/2
(D) (-4y^2)/1-2y
(E) -2y


A. Used back solving starting w/ choice A.

x = sqrt(4xy-4y^2) --> given
let x = 2y
Is 2y = sqrt (8y^2-4y^2)?
Is 2y = sqrt (4y^2)? Yes.
VP
VP
User avatar
Joined: 08 Jun 2005
Posts: 1146
Followers: 6

Kudos [?]: 136 [0], given: 0

Re: Equation [#permalink] New post 17 Nov 2007, 00:41
johnrb wrote:
yogachgolf wrote:
If x is not equal to zero, and x = sqrt(4xy-4y^2), then in terms of y, x =

(A) 2y
(B) y
(C) y/2
(D) (-4y^2)/1-2y
(E) -2y


Square both sides:

x^2 = 4xy - 4y^2

Bring everything to the left:

x^2 - 4xy + 4y^2 = 0

Factor:

(x - 2y)^2 = 0

So x = 2y.


Perfect !

:)
Director
Director
User avatar
Joined: 26 Feb 2006
Posts: 905
Followers: 4

Kudos [?]: 64 [0], given: 0

Re: Equation [#permalink] New post 18 Nov 2007, 11:48
johnrb wrote:
yogachgolf wrote:
If x is not equal to zero, and x = sqrt(4xy-4y^2), then in terms of y, x =

(A) 2y
(B) y
(C) y/2
(D) (-4y^2)/1-2y
(E) -2y


Square both sides:

x^2 = 4xy - 4y^2

Bring everything to the left:

x^2 - 4xy + 4y^2 = 0

Factor:

(x - 2y)^2 = 0

So x = 2y.


this is an equation question, and asking the value of x in terms of y. so solving the equation would be the correct approach.
Re: Equation   [#permalink] 18 Nov 2007, 11:48
Display posts from previous: Sort by

If x is not equal to zero, and x = sqrt(4xy-4y^2), then in

  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®.