Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 04 May 2015, 08:22

### 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

# what is the value of x y

Author Message
TAGS:
Director
Joined: 19 Mar 2007
Posts: 524
Followers: 2

Kudos [?]: 8 [0], given: 0

what is the value of x y [#permalink]  11 Jun 2007, 06:03
what is the value of x – y?

Last edited by nick_sun on 28 Jun 2008, 01:14, edited 1 time in total.
SVP
Joined: 01 May 2006
Posts: 1805
Followers: 8

Kudos [?]: 99 [0], given: 0

(A) for me

x-y = ?

From 1
(x^2 – y^2) / (x + y) = 4
<=> (x-y) * (x+y) / (x+y) = 4
<=> x - y = 4

SUFF.

From 2
x + y = 7 >>> we can do nothing with it...

Picking numbers to be sure?
o If x=3 and y = 4, then x-y = -1
o If x=4 and y = 3, then x-y = 1

INSUFF.
Director
Joined: 19 Mar 2007
Posts: 524
Followers: 2

Kudos [?]: 8 [0], given: 0

Thanks, Fig! The answer is A. Can't make myself factorize the quadratic equations
CEO
Joined: 17 May 2007
Posts: 2994
Followers: 59

Kudos [?]: 467 [0], given: 210

Shouldn't the answer be C ?

Otherwise how would u know that x+y not equal to 0 ?

I remember a similar question in one of the challenges.
CEO
Joined: 17 May 2007
Posts: 2994
Followers: 59

Kudos [?]: 467 [0], given: 210

I retract my earlier comment. x and y are positive hence A is indeed sufficient.
SVP
Joined: 01 May 2006
Posts: 1805
Followers: 8

Kudos [?]: 99 [0], given: 0

bsd_lover wrote:
Shouldn't the answer be C ?

Otherwise how would u know that x+y not equal to 0 ?

I remember a similar question in one of the challenges.

x+y must be different from 0 because the equation exists and is stated ... It's true that in the real GMAT, it will be stated that x+y != 0 to avoid any confusion.

We just have to remove a solution to the equation that does x+y=0 if such a solution exists.

Here, we arrive to x-y = 4 and we should keep in mind that the intersection of the 2 lines x-y = 4 and x+y = 0 must be removed.... But for this problem, we do not care it
SVP
Joined: 01 May 2006
Posts: 1805
Followers: 8

Kudos [?]: 99 [0], given: 0

bsd_lover wrote:
I retract my earlier comment. x and y are positive hence A is indeed sufficient.

Also yes
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5078
Location: Singapore
Followers: 22

Kudos [?]: 184 [0], given: 0

St1:
(x+y)(x-y)/(x+y) = 4
x-y = 4 --> sufficient.

St2:
x+y = 7, but there are many possible (x,y) solutions each giving different x-y results. --> insufficient.

ans A
Manager
Joined: 17 Oct 2006
Posts: 52
Followers: 0

Kudos [?]: 1 [0], given: 0

my vote is for A too.
Director
Joined: 30 Nov 2006
Posts: 591
Location: Kuwait
Followers: 12

Kudos [?]: 169 [0], given: 0

(1) (x^2 – y^2) / (x + y) = 4
------------------------------------
(x^2 - y^2) = (x-y) (x+y)

Thus: (x^2 – y^2) / (x + y) = (x - y) = 4

statement 1 is sufficient

(2) x + y = 7
-----------------
Two variables one equation .. we can conclude nothing about x - y ..

statement 2 is insufficient

Similar topics Replies Last post
Similar
Topics:
1 What is the value of x - y? 1 18 Nov 2013, 06:25
2 What is value of x - y? 8 06 Apr 2013, 10:04
5 What is the value of x + y? 5 02 Apr 2013, 09:05
What is the value of x – y ? 1 27 May 2012, 08:11
What is the value of x-y? 2 29 May 2007, 05:19
Display posts from previous: Sort by