Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 27 May 2017, 04:22

### 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

# Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0

Author Message
TAGS:

### Hide Tags

Manager
Status: Preparing myself to break the sound( 700 )-barrier!
Joined: 15 Feb 2011
Posts: 209
Schools: Texas A&M - Mays; PennState - Smeal; Purdue - Krannert; JohnsHopkins - Carey; Vanderbilt - Owen; WakeForest - Babcock; UBC - Sauder
WE 1: Financial Analyst/Financial Management Trainer - BRAC Afghanistan - 13 months
WE 2: Business Proposal Coordinator - MiDS, Inc. (in Kabul, Afghanistan) - 4 Months (did quit the job bcoz of security concerns)
WE 3: Readers For Readers (A Social Impact Generating Organization) - Co-Founder
Followers: 7

Kudos [?]: 76 [0], given: 136

Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0 [#permalink]

### Show Tags

29 Apr 2011, 07:21
00:00

Difficulty:

15% (low)

Question Stats:

74% (01:27) correct 26% (00:48) wrong based on 151 sessions

### HideShow timer Statistics

Does x = y?

(1) x^2 - y^2 = 0
(2) (x - y)^2 = 0
[Reveal] Spoiler: OA

Last edited by Bunuel on 15 Oct 2013, 09:36, edited 1 time in total.
Renamed the topic and edited the question.
Director
Joined: 01 Feb 2011
Posts: 755
Followers: 14

Kudos [?]: 125 [1] , given: 42

### Show Tags

29 Apr 2011, 08:01
1
KUDOS
1. Not sufficient
x^2 = y^2
But that doesnt mean x = y.
x can be y or x can be -y
2. Sufficient

x = y is only solution that can satisfy (x-y)^2=0.

Posted from my mobile device
Manager
Status: Preparing myself to break the sound( 700 )-barrier!
Joined: 15 Feb 2011
Posts: 209
Schools: Texas A&M - Mays; PennState - Smeal; Purdue - Krannert; JohnsHopkins - Carey; Vanderbilt - Owen; WakeForest - Babcock; UBC - Sauder
WE 1: Financial Analyst/Financial Management Trainer - BRAC Afghanistan - 13 months
WE 2: Business Proposal Coordinator - MiDS, Inc. (in Kabul, Afghanistan) - 4 Months (did quit the job bcoz of security concerns)
WE 3: Readers For Readers (A Social Impact Generating Organization) - Co-Founder
Followers: 7

Kudos [?]: 76 [0], given: 136

### Show Tags

29 Apr 2011, 09:34
@ Shubhabsh Da'

I am confused with the answer; and the explanation as well.

Because, in statement 1, if we add y^2 on both sides, we get x^2 = y^2. Then, if we square root both the sides of the equation, we get x = y (no matter whether they are positive or negative). So, this is sufficient and is eliminating option B, C, and E.

Then, in the statement 2, if we square root both the sides of the equation, we get x - y = 0, or x = y (no matter whether they are positive or negative).

Therefore, my answer is D. However, Kaplan Premier 2011 shows the answer as B and explains it thereby.

Director
Joined: 01 Feb 2011
Posts: 755
Followers: 14

Kudos [?]: 125 [0], given: 42

### Show Tags

29 Apr 2011, 15:52
@Schawjibb,

square root of x^2 = could be x or -x ( not just x)

in other words square root of x^2 = |x| = +-x

so when you take square root on both sides , you will have +- on both sides. not enough to find the sign of the variable.

=> x = y or x = -y

Eg: \sqrt{(x^2)} = 25 => |x| = 5 =>x = +5 or -5

Hope it helps.

Schawjibb wrote:
@ Shubhabsh Da'

I am confused with the answer; and the explanation as well.

Because, in statement 1, if we add y^2 on both sides, we get x^2 = y^2. Then, if we square root both the sides of the equation, we get x = y (no matter whether they are positive or negative). So, this is sufficient and is eliminating option B, C, and E.

Then, in the statement 2, if we square root both the sides of the equation, we get x - y = 0, or x = y (no matter whether they are positive or negative).

Therefore, my answer is D. However, Kaplan Premier 2011 shows the answer as B and explains it thereby.

Manager
Joined: 09 Aug 2010
Posts: 107
Followers: 1

Kudos [?]: 46 [0], given: 7

### Show Tags

30 Apr 2011, 02:43
1
This post was
BOOKMARKED
Schawjibb wrote:
I found this question in Kaplan Premier 2011. I am confused with their answer and its explanation (or, may be I am wrong). Can anyone come up with an answer supported by precise explanation?

Q. Does x = y?
(1) x^2 - y^2 = 0
(2) (x - y)^2 = 0

Solution:
Statement 1:
$$x^2-y^2=0$$
$$x^2=y^2$$
Squaring both sides, would result to two solutions: x= y OR x=-y. So, INSUFFICIENT!

Statement 2:
$$(x-y)^2=0$$
To get a 0, x-y must be equal to 0.
$$x=y$$
SUFFICIENT!

VP
Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 1334
Followers: 17

Kudos [?]: 254 [0], given: 10

### Show Tags

03 May 2011, 11:21
Schawjibb wrote:
@ Spidy001

Could you please help me in one regard? I need a resource (book/forum discussion) from where I can really learn how to solve a DS problem systematically and in minimum time.

Background: I have started going through the DS section from Kaplan Premier 2011 yesterday. And the result of yesterday's (first-time) practice was devastating. 13 out of 20 were incorrect. And no question was answered in less than 2 minutes! I am just drowning into frustration.......

My 2 cents on this.

See the best resources are the OG's, GMAT Club Math Forum and the MGMAT tests.

Seeing the problem that you are facing right now,probably you should brush up your basics first.Then start with OG and subsequently move on to higher difficulty level numerical s.
_________________

Visit -- http://www.sustainable-sphere.com/
Promote Green Business,Sustainable Living and Green Earth !!

Manager
Status: Preparing myself to break the sound( 700 )-barrier!
Joined: 15 Feb 2011
Posts: 209
Schools: Texas A&M - Mays; PennState - Smeal; Purdue - Krannert; JohnsHopkins - Carey; Vanderbilt - Owen; WakeForest - Babcock; UBC - Sauder
WE 1: Financial Analyst/Financial Management Trainer - BRAC Afghanistan - 13 months
WE 2: Business Proposal Coordinator - MiDS, Inc. (in Kabul, Afghanistan) - 4 Months (did quit the job bcoz of security concerns)
WE 3: Readers For Readers (A Social Impact Generating Organization) - Co-Founder
Followers: 7

Kudos [?]: 76 [0], given: 136

### Show Tags

03 May 2011, 21:19
@ Amit

Thanks a lot! I think my basic problem pertaining to DS is with Number Properties. Because, in other fields I feel myself comfortable as long as the math part is concerned. Do you think MGMAT Number Properties book will suffice? Suggestions are highly appreciated?
Current Student
Joined: 06 Sep 2013
Posts: 2005
Concentration: Finance
Followers: 68

Kudos [?]: 643 [0], given: 355

Re: Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0 [#permalink]

### Show Tags

15 Oct 2013, 09:31
Schawjibb wrote:
I found this question in Kaplan Premier 2011. I am confused with their answer and its explanation (or, may be I am wrong). Can anyone come up with an answer supported by precise explanation?

Q. Does x = y?
(1) x^2 - y^2 = 0
(2) (x - y)^2 = 0

Hi there, let me take a bite a this one.

So does x = y?

From Statement 1:

x^2 - y^2 = 0

This means that Abs (X) = Abs (Y)
But could be that x = -y, or x = y
Hence Insuff

From Statement 2

(x-y)^2 = 0
(x-y) = 0
So x = y
Suff

Cheers
J

Last edited by jlgdr on 15 Oct 2013, 10:09, edited 1 time in total.
Math Expert
Joined: 02 Sep 2009
Posts: 38910
Followers: 7741

Kudos [?]: 106296 [0], given: 11620

Re: Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0 [#permalink]

### Show Tags

15 Oct 2013, 09:38
jlgdr wrote:
Schawjibb wrote:
I found this question in Kaplan Premier 2011. I am confused with their answer and its explanation (or, may be I am wrong). Can anyone come up with an answer supported by precise explanation?

Q. Does x = y?
(1) x^2 - y^2 = 0
(2) (x - y)^2 = 0

Hi there, let me take a bite a this one.

So does x = y?

From Statement 1:

x^2 - y^2 = 0

This means that Abs (X) = Abs (Y)
But could be that x = -y, or x = y
Hence Insuff

From Statement 2

(x-y)^2 = 0
(x+y)(x-y) = 0
x = -y or x = y
So Insuff

From Statements 1 and 2 together:
We have exactly the same information, hence IMHO E is the correct answer

Cheers
J

That's not correct.

Does x = y?

(1) x^2 - y^2 = 0 --> x^2=y^2 --> x=y or x=-y. Not sufficient.

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

_________________
Current Student
Joined: 06 Sep 2013
Posts: 2005
Concentration: Finance
Followers: 68

Kudos [?]: 643 [0], given: 355

Re: Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0 [#permalink]

### Show Tags

15 Oct 2013, 10:08
Bunuel wrote:
jlgdr wrote:
Schawjibb wrote:
I found this question in Kaplan Premier 2011. I am confused with their answer and its explanation (or, may be I am wrong). Can anyone come up with an answer supported by precise explanation?

Q. Does x = y?
(1) x^2 - y^2 = 0
(2) (x - y)^2 = 0

Hi there, let me take a bite a this one.

So does x = y?

From Statement 1:

x^2 - y^2 = 0

This means that Abs (X) = Abs (Y)
But could be that x = -y, or x = y
Hence Insuff

From Statement 2

(x-y)^2 = 0
(x+y)(x-y) = 0
x = -y or x = y
So Insuff

From Statements 1 and 2 together:
We have exactly the same information, hence IMHO E is the correct answer

Cheers
J

That's not correct.

Does x = y?

(1) x^2 - y^2 = 0 --> x^2=y^2 --> x=y or x=-y. Not sufficient.

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

Apologies for that. Yes that's in fact correct.
Thanks for pointing out.
Cheers
J
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15478
Followers: 651

Kudos [?]: 209 [0], given: 0

Re: Does x = y ? [#permalink]

### Show Tags

11 Oct 2015, 04:13
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.
_________________
Senior Manager
Status: DONE!
Joined: 05 Sep 2016
Posts: 409
Followers: 3

Kudos [?]: 16 [0], given: 283

Re: Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0 [#permalink]

### Show Tags

16 Sep 2016, 18:00
B is correct

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

We have no way to know with certainty the values of x and y. Y could be x negated or the same value as x. Thus, INSUFFICIENT

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

SUFFICIENT
Re: Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0   [#permalink] 16 Sep 2016, 18:00
Similar topics Replies Last post
Similar
Topics:
Is x^2 - y^2 > 0? 1 22 Mar 2017, 02:01
3 Does x = y ? (1) x^2 - y^2 = 0 (2) (x + y)^2 = 0 3 11 Oct 2015, 14:52
4 What is the value of x^2-y^2? (1) x+y=0 (2) x-y=2 3 24 Apr 2016, 05:31
17 Is x > y^2? (1) x > y+5 (2) x^2-y^2 = 0 15 13 Dec 2015, 04:29
13 Is x > y^2? 1. x > y + 5 2. x^2 - y^2 = 0 8 22 Jun 2012, 07:35
Display posts from previous: Sort by

# Does x = y? (1) x^2 - y^2 = 0 (2) (x - y)^2 = 0

 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®.