It is currently 19 Nov 2017, 13:25

### 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 2x^2 - y^2 = 2xy, then (x+y)^2 =

Author Message
TAGS:

### Hide Tags

Retired Moderator
Status: Darden Class of 2013
Joined: 28 Jul 2009
Posts: 1834

Kudos [?]: 398 [1], given: 37

Schools: University of Virginia
If 2x^2 - y^2 = 2xy, then (x+y)^2 = [#permalink]

### Show Tags

10 May 2010, 17:45
1
KUDOS
7
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

73% (01:21) correct 27% (02:20) wrong based on 454 sessions

### HideShow timer Statistics

If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2
[Reveal] Spoiler: OA

_________________

Kudos [?]: 398 [1], given: 37

Senior Manager
Joined: 12 Jan 2010
Posts: 255

Kudos [?]: 90 [2], given: 28

Schools: DukeTuck,Kelogg,Darden

### Show Tags

10 May 2010, 17:50
2
KUDOS
Its B

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

Add x^2 on both sides we get

2x^2 +x^2 = x^2 +y^2 +2xy
3x^2 = (x+y)^2
_________________

Run towards the things that make you uncomfortable daily. The greatest risk is not taking risks
http://gmatclub.com/forum/from-690-to-730-q50-v38-97356.html

Kudos [?]: 90 [2], given: 28

Math Expert
Joined: 02 Sep 2009
Posts: 42259

Kudos [?]: 132708 [1], given: 12335

### Show Tags

10 May 2010, 17:53
1
KUDOS
Expert's post
4
This post was
BOOKMARKED
bakfed wrote:
If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2

OA
[Reveal] Spoiler:
B

Given: $$2xy=2x^2-y^2$$.

$$(x+y)^2 =x^2+2xy+y^2$$ --> substitute $$2xy$$ --> $$(x+y)^2 =x^2+(2x^2 - y^2)+y^2=3x^2$$.

_________________

Kudos [?]: 132708 [1], given: 12335

Manager
Joined: 16 Feb 2010
Posts: 179

Kudos [?]: 34 [1], given: 17

### Show Tags

18 May 2010, 09:17
1
KUDOS
bakfed wrote:
If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2

OA
[Reveal] Spoiler:
B

here we have to find the value of x^2 +y^2 +2xy in which 2xy
=2x^2 -y^2 (given ) hence ans is 3x^2.

Kudos [?]: 34 [1], given: 17

Non-Human User
Joined: 09 Sep 2013
Posts: 15657

Kudos [?]: 282 [0], given: 0

Re: If 2x^2 - y^2 = 2xy, then (x+y)^2 = [#permalink]

### Show Tags

03 Nov 2014, 05:03
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 [?]: 282 [0], given: 0

Non-Human User
Joined: 09 Sep 2013
Posts: 15657

Kudos [?]: 282 [0], given: 0

Re: If 2x^2 - y^2 = 2xy, then (x+y)^2 = [#permalink]

### Show Tags

10 Apr 2016, 06:19
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 [?]: 282 [0], given: 0

Intern
Joined: 20 Mar 2017
Posts: 1

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

Re: If 2x^2 - y^2 = 2xy, then (x+y)^2 = [#permalink]

### Show Tags

24 Mar 2017, 05:30
Quite straight forward question

step 1:
(x+Y)^2 = X^2 +2xy + y^2

step 2:
now substitute 2xy from the equation.

(x+Y)^2 = X^2 +2x^2-y^2+y^2.

-y^2 and Y^2 cancels out

we are left with x^2+2X^2= 3X^2 Hence B.

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

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 1806

Kudos [?]: 922 [1], given: 3

Location: United States (CA)
Re: If 2x^2 - y^2 = 2xy, then (x+y)^2 = [#permalink]

### Show Tags

27 Mar 2017, 17:22
1
KUDOS
Expert's post
bakfed wrote:
If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2

We see that we are looking for the value of (x + y)^2 = x^2 + y^2 + 2xy.

We also see that 2x^2 - y^2 = 2xy; thus we can substitute for 2xy and we have:

x^2 + y^2 + 2x^2 - y^2 = 3x^2

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 922 [1], given: 3

Director
Joined: 12 Nov 2016
Posts: 794

Kudos [?]: 36 [0], given: 165

Re: If 2x^2 - y^2 = 2xy, then (x+y)^2 = [#permalink]

### Show Tags

24 Apr 2017, 20:38
bakfed wrote:
If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2

An efficient way to solve this question is to foil (x + y)^2 and substitute- foiling is critical

X^2 + (2x^2 - y^2) + y^2

Kudos [?]: 36 [0], given: 165

Re: If 2x^2 - y^2 = 2xy, then (x+y)^2 =   [#permalink] 24 Apr 2017, 20:38
Display posts from previous: Sort by