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

 It is currently 21 Oct 2019, 15:48 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58396
If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags 00:00

Difficulty:   95% (hard)

Question Stats: 28% (02:20) correct 72% (02:25) wrong based on 85 sessions

HideShow timer Statistics

If xy > 0, does (x – 1)(y – 1) = 2 ?

(1) x + y = –1
(2) x = y

_________________
CEO  D
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2978
Location: India
GMAT: INSIGHT
Schools: Darden '21
WE: Education (Education)
Re: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags

Bunuel wrote:
If xy > 0, does (x – 1)(y – 1) = 2 ?

(1) x + y = –1
(2) x = y

Question : does (x – 1)(y – 1) = 2 ?
Question : does xy - (x+y) +1 = 2 ?
Question : does xy - (x+y) = 1 ?

Statement 1: x+y = -1

but we dont know about xy hence
NOT SUFFICIENT

Statement 2: x = y
but we dont know about value of x hence
NOT SUFFICIENT

Combining the two statements
x = y = -1/2
SUFFICIENT

_________________
Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION
Intern  B
Joined: 14 Nov 2012
Posts: 23
GMAT 1: 740 Q51 V38 Re: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags

Bunuel wrote:
If xy > 0, does (x – 1)(y – 1) = 2 ?

(1) x + y = –1
(2) x = y

(x – 1)(y – 1) = 2
=> xy - x - y -1 = 0
=> xy = 1 +x +y
So the question basically is whether xy = 1 +x +y

(1) x + y = –1

=> xy = 0 (which will not happen as xy >0)
Sufficient

(2) x = y

=> x^2 = 1 + 2x
=> x^2 - 2x -1 = 0
=> We surely can find 2 values of x that satisfies above equation.
So, it depends on x and y that the condition is met or not.
Insufficient.

So A is the answer
BSchool Moderator B
Joined: 29 Aug 2016
Posts: 104
Location: India
Re: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags

Bunuel wrote:
If xy > 0, does (x – 1)(y – 1) = 2 ?

(1) x + y = –1
(2) x = y

D

Not sure if the solution is correct, but here is how I did it:

(1) Solving for the equation:
1 + xy - (x+y) = 2, this comes out to be xy=0 which doesn't confirm with the given situation. Hence,

SUFFICIENT

2) putting x=y in the given, we get x=y= 1+ sqrt 2 or 1-sqrt 2. Both give you 2 as an answer.

SUFFICIENT

Hence, D.

Sent from my iPhone using GMAT Club Forum mobile app
Intern  B
Joined: 24 Jan 2015
Posts: 48
Location: India
Re: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags

@Bunuel- Again different answers here, could you provide the correct answer?
Math Expert V
Joined: 02 Sep 2009
Posts: 58396
Re: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags

1
3
Amerendra wrote:
@Bunuel- Again different answers here, could you provide the correct answer?

The OA is under the spoiler in the original post and it's A.

If xy > 0, does (x – 1)(y – 1) = 2 ?

Does (x – 1)(y – 1) = 2 ?
Does xy - x - y + 1 = 2?
Does xy - x - y = 1?
Does xy - (x + y) = 1?

(1) x + y = –1. Substitute into the question: does xy + 1 = 1? Or: does xy = 0? We are given that xy > 0, so the answer to the question is NO. Sufficient.

(2) x = y. Substitute into the original question: does (x – 1)^2 = 2 ? Does $$x – 1=+/-\sqrt{2}$$? Does $$x=1+/-\sqrt{2}$$? We don't know that. Not sufficient.

_________________
Non-Human User Joined: 09 Sep 2013
Posts: 13382
Re: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y  [#permalink]

Show Tags

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: If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y   [#permalink] 30 Oct 2018, 02:38
Display posts from previous: Sort by

If xy > 0, does (x – 1)(y – 1) = 2 ? (1) x + y = –1 (2) x = y

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  