Author 
Message 
TAGS:

Hide Tags

Manager
Status: Preparing myself to break the sound( 700 )barrier!
Affiliations: IFC  Business Edge, Bangladesh Enterprise Institute
Joined: 15 Feb 2011
Posts: 209

Does x = y? (1) x^2  y^2 = 0 (2) (x  y)^2 = 0 [#permalink]
Show Tags
29 Apr 2011, 07:21
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
Official Answer and Stats are available only to registered users. Register/ Login.
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: 753

Re: Please help! [#permalink]
Show Tags
29 Apr 2011, 08:01
1
This post received 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 (xy)^2=0.
My answer is B.
Posted from my mobile device



Manager
Status: Preparing myself to break the sound( 700 )barrier!
Affiliations: IFC  Business Edge, Bangladesh Enterprise Institute
Joined: 15 Feb 2011
Posts: 209

Re: Please help! [#permalink]
Show Tags
29 Apr 2011, 09:34
@ Shubhabsh Da'I am confused with the answer; and the explanation as well. My answer is D. 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. Any inputs, please?



Director
Joined: 01 Feb 2011
Posts: 753

Re: Please help! [#permalink]
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. My answer is D. 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. Any inputs, please?



Manager
Joined: 09 Aug 2010
Posts: 107

Re: Please help! [#permalink]
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 Thanks in advance! Solution: Statement 1: \(x^2y^2=0\) \(x^2=y^2\) Squaring both sides, would result to two solutions: x= y OR x=y. So, INSUFFICIENT! Statement 2: \((xy)^2=0\) To get a 0, xy must be equal to 0. \(x=y\) SUFFICIENT! Answer: B



VP
Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 1325

Re: Please help! [#permalink]
Show Tags
03 May 2011, 11:21
Schawjibb wrote: @ Spidy001Could 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 (firsttime) 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.sustainablesphere.com/ Promote Green Business,Sustainable Living and Green Earth !!



Manager
Status: Preparing myself to break the sound( 700 )barrier!
Affiliations: IFC  Business Edge, Bangladesh Enterprise Institute
Joined: 15 Feb 2011
Posts: 209

Re: Please help! [#permalink]
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: 1997
Concentration: Finance

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 Thanks in advance! 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 (xy)^2 = 0 (xy) = 0 So x = y Suff Answer is B Cheers J
Last edited by jlgdr on 15 Oct 2013, 10:09, edited 1 time in total.



Math Expert
Joined: 02 Sep 2009
Posts: 40413

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 Thanks in advance! 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 (xy)^2 = 0 (x+y)(xy) = 0 x = y or x = y So InsuffFrom 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 > xy=0 > x=y. Sufficient. Answer: B.
_________________
New to the Math Forum? Please read this: All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Current Student
Joined: 06 Sep 2013
Posts: 1997
Concentration: Finance

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 Thanks in advance! 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 (xy)^2 = 0 (x+y)(xy) = 0 x = y or x = y So InsuffFrom 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 > xy=0 > x=y. Sufficient. Answer: B. Apologies for that. Yes that's in fact correct. Thanks for pointing out. Cheers J



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16581

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.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



Senior Manager
Status: DONE!
Joined: 05 Sep 2016
Posts: 409

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) (xy)^2 = 0 =(xy) = 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







