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

 It is currently 25 May 2017, 21:26

### 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
Intern
Joined: 12 May 2007
Posts: 14
Followers: 0

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

What is the value of x-y? [#permalink]

### Show Tags

29 May 2007, 06:19
00:00

Difficulty:

(N/A)

Question Stats:

67% (01:39) correct 33% (05:47) wrong based on 4 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

I am struggling with this one. Any Help?

What is the value of x-y?

1) x=y+3
2) x^2-2xy+y^2=9

I get the answer somewhat, but statement #2 is confusing me bc I though that sqrt(9) = POSITIVE 3 only, not +3 or -3. Because once you factor out the statement and get (x-y)(x-y)=9 --> (x-y)^2=9, the answer says by squaring both sides you get two possible solutions, x-y=3 and x-y=-3, but isnt the sqrt of both sides leaving you with x-y=+3 bc its only a positive root? Any ideas on this one this whole sqroot + versus - business? Thanks
SVP
Joined: 01 May 2006
Posts: 1796
Followers: 9

Kudos [?]: 154 [0], given: 0

### Show Tags

29 May 2007, 07:11
It's (A)

Why not (D)?
o Sqrt(x^2-2xy+y^2) = Sqrt( (x-y)^2) = |x-y|

So, |x-y| = 3 <=> x-y = 3 or x-y = -3

This is one way to figure it out and to remember it
Intern
Joined: 22 Mar 2007
Posts: 8
Followers: 0

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

### Show Tags

29 May 2007, 12:07
Thanks Fig ,nice logic

and dear americo

you can imagine (x-y) as just one variable like Z so

(Z)^2=9 then z can be +3 or -3. and the question asks for value of x-y.

although Fig's explanation is much better but may be its another way of thinking about it.
29 May 2007, 12:07
Display posts from previous: Sort by