GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 19 Apr 2019, 10:05

### 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

# Is x = y? (1) x^2 = xy (2) x^2 = y^2

Author Message
TAGS:

### Hide Tags

Current Student
Joined: 12 Aug 2015
Posts: 2613
Schools: Boston U '20 (M)
GRE 1: Q169 V154
Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

Updated on: 10 Apr 2016, 09:53
1
1
00:00

Difficulty:

55% (hard)

Question Stats:

52% (01:08) correct 48% (01:12) wrong based on 75 sessions

### HideShow timer Statistics

Is x = y?

(1) x^2 = xy
(2) x^2 = y^2

_________________

Originally posted by stonecold on 09 Apr 2016, 22:10.
Last edited by Bunuel on 10 Apr 2016, 09:53, edited 1 time in total.
Renamed the topic and edited the question.
SC Moderator
Joined: 13 Apr 2015
Posts: 1685
Location: India
Concentration: Strategy, General Management
GMAT 1: 200 Q1 V1
GPA: 4
WE: Analyst (Retail)
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

09 Apr 2016, 22:26
4
2
St1: x^2 - xy = 0
x(x - y) = 0 --> x = 0 or x = y
If x = 0 then y can be any value.
Not sufficient

St2: x^2 - y^2 = 0
(x + y)(x - y) = 0 --> x = y or x = -y
Not sufficient

Combining St1 and St2, we can confirm that x will always be equal to y
Sufficient

##### General Discussion
CEO
Joined: 12 Sep 2015
Posts: 3584
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

10 Apr 2016, 07:31
stonecold wrote:
Is x=y?
[A] x² = xy
[B] x² = y²

Vyshak's solution is great, so I won't re-answer the question.
I just want to point out that the intended TRAP here is that some people will incorrectly take the equation x² = xy and divide both sides by x to get x = y
People who do that will incorrectly conclude that the answer is A.
The problem with taking the equation x² = xy and dividing both sides by x is that you may be dividing both sides by zero, which is a big no-no.
Likewise, if we take this valid equation, (2)(0) = (1)(0) and divide both sides by 0, we can't then conclude that 2 = 1

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Board of Directors
Joined: 17 Jul 2014
Posts: 2556
Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

11 Oct 2016, 07:51
1
stonecold wrote:
Is x = y?

(1) x^2 = xy
(2) x^2 = y^2

1. x^2 - xy = 0
x(x-y)=0
x=0, x=y - 2 outcomes, not sufficient.

2. x^2 = y^2
x=2, y=2 - yes
x=-2, y=2 - no
not sufficient.

1+2
x=0 -> y=0 - ok
x=y -> ok

sufficient.

Manager
Joined: 27 Dec 2016
Posts: 232
Concentration: Marketing, Social Entrepreneurship
GPA: 3.65
WE: Marketing (Education)
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

18 Aug 2017, 05:27
GMATPrepNow wrote:
stonecold wrote:
Is x=y?
[A] x² = xy
x² = y²

Vyshak's solution is great, so I won't re-answer the question.
I just want to point out that the intended TRAP here is that some people will incorrectly take the equation x² = xy and divide both sides by x to get x = y
People who do that will incorrectly conclude that the answer is A.
The problem with taking the equation x² = xy and dividing both sides by x is that you may be dividing both sides by zero, which is a big no-no.
Likewise, if we take this valid equation, (2)(0) = (1)(0) and divide both sides by 0, we can't then conclude that 2 = 1

Cheers,
Brent

Dear Brent [b]GMATPrepNow ,

Can we conclude that, for this similar questions, it is easier if we use algebraic approach?

_________________
There's an app for that - Steve Jobs.
Senior Manager
Joined: 06 Jul 2016
Posts: 364
Location: Singapore
Concentration: Strategy, Finance
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

18 Aug 2017, 06:29
stonecold wrote:
Is x = y?

(1) x^2 = xy
(2) x^2 = y^2

1) $$x^2$$ = xy
=> x = 0 or x = y
Insufficient.

2) $$x^2$$ = $$y^2$$
x = y OR x = -y
=> x = 2 , y = 2
OR x = -2 , y = 2
Insufficient.

1+2)
x = y
Sufficient.

_________________
Put in the work, and that dream score is yours!
Non-Human User
Joined: 09 Sep 2013
Posts: 10552
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2  [#permalink]

### Show Tags

19 Apr 2019, 05:26
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.
_________________
Re: Is x = y? (1) x^2 = xy (2) x^2 = y^2   [#permalink] 19 Apr 2019, 05:26
Display posts from previous: Sort by