It is currently 22 Nov 2017, 01:06

### 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≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x =

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 19 Oct 2010
Posts: 252

Kudos [?]: 91 [0], given: 27

Location: India
GMAT 1: 560 Q36 V31
GPA: 3
If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 07:34
2
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

70% (00:55) correct 30% (01:51) wrong based on 70 sessions

### HideShow timer Statistics

If x≠0 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
[Reveal] Spoiler: OA

_________________

petrifiedbutstanding

Kudos [?]: 91 [0], given: 27

Manager
Joined: 11 Feb 2011
Posts: 129

Kudos [?]: 254 [1], given: 21

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 07:49
1
KUDOS
@petrifiedbutstanding:-

Well it means :
Squaring we get:
x^2 =4y(x-y)
Assume X^2=m >>>>>>>>>>>1
Than ,m=4y(m^1/2-y)
on solving:m-4y(m)^1/2+4y^2=0 >> quadratic in y s solve for y.
Y comes out to be =(m^1/2)/2

Hence,put m =x^2 from 1.

So x=2y

The answer shd be 2y. i.e A.

Pls confirm it .
_________________

target:-810 out of 800!

Kudos [?]: 254 [1], given: 21

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 1965

Kudos [?]: 2097 [1], given: 376

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 07:51
1
KUDOS
2
This post was
BOOKMARKED
petrifiedbutstanding wrote:
If x≠0 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

$$x = \sqrt{4xy-4y^2}$$
Square both sides;

$$x^2 = 4xy-4y^2$$
$$x^2+4y^2-4xy=0$$
$$(x-2y)^2=0$$ Note: $$(a-b)^2=a^2+b^2-2ab$$
$$(x-2y)^2=0$$
$$x-2y=0$$
$$x=2y$$

Ans: "A"
_________________

Kudos [?]: 2097 [1], given: 376

Manager
Joined: 11 Feb 2011
Posts: 129

Kudos [?]: 254 [0], given: 21

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 07:53
If i am correct donot hesitate to kudo me .

Your support is required to bang GMAT.
_________________

target:-810 out of 800!

Kudos [?]: 254 [0], given: 21

Manager
Joined: 11 Feb 2011
Posts: 129

Kudos [?]: 254 [0], given: 21

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 07:57
Thnkss Flukee!!:)
_________________

target:-810 out of 800!

Kudos [?]: 254 [0], given: 21

Director
Joined: 01 Feb 2011
Posts: 725

Kudos [?]: 146 [0], given: 42

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 13:27
x^2 = 4xy-4(y^2) => (x-2y)^2 = 0

=> x = 2y

Kudos [?]: 146 [0], given: 42

TOEFL Forum Moderator
Joined: 16 Nov 2010
Posts: 1603

Kudos [?]: 601 [0], given: 40

Location: United States (IN)
Concentration: Strategy, Technology
Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

26 Mar 2011, 18:20
x = sqrt{4xy-4y^2}

Squaring both side :

=> x^2 = 4xy - 4y^2

Substituting answer choices, e.g., choice A :

=> (2y)^2 = 4*2y*y - 4y^2

=> 4y^2 - 8y^2 = - 4y^2

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

=> (x -2y)^2 = 0

=> x = 2y

Note - I thought simplifying further would be faster and more accurate than plugging the answer choices in this case, but situations may vary.

Also, the OA seems to be wrong.
_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Kudos [?]: 601 [0], given: 40

Non-Human User
Joined: 09 Sep 2013
Posts: 15562

Kudos [?]: 283 [0], given: 0

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x = [#permalink]

### Show Tags

18 Jul 2016, 07:04
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Kudos [?]: 283 [0], given: 0

Re: If x≠0 and x = (4xy-4y^2)^1/2, then, in terms of y, x =   [#permalink] 18 Jul 2016, 07:04
Display posts from previous: Sort by