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

 It is currently 04 Jul 2015, 08:23

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

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

Author Message
TAGS:
Manager
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]  16 Nov 2007, 11:19
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
Joined: 01 Oct 2007
Posts: 87
Followers: 0

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

Re: Equation [#permalink]  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
Joined: 29 Mar 2007
Posts: 2585
Followers: 17

Kudos [?]: 243 [0], given: 0

Re: Equation [#permalink]  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
Joined: 09 Aug 2006
Posts: 763
Followers: 1

Kudos [?]: 76 [0], given: 0

Re: Equation [#permalink]  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
Joined: 08 Jun 2005
Posts: 1146
Followers: 6

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

Re: Equation [#permalink]  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
Joined: 26 Feb 2006
Posts: 905
Followers: 4

Kudos [?]: 58 [0], given: 0

Re: Equation [#permalink]  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
Similar topics Replies Last post
Similar
Topics:
Is x + |x| zero for all negative x ? 3 19 Sep 2013, 08:50
If x is not equal to zero, is 1/x > 1? 1) y/x > y 2) 5 25 Sep 2006, 11:26
x not equal zero sqrt(x^2)/x = ?? -1 0 1 x |x|/x 3 07 May 2006, 16:58
1 x not equal to 0 x=sqrt(4xy-4y^2) then in terms of y, x= a) 3 21 Feb 2006, 11:07
If x not eq to 0 and x=sqrt(4xy-4y^2) , then, in terms of y, 8 17 Jan 2006, 04:15
Display posts from previous: Sort by