It is currently 22 Mar 2018, 03:19

### 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

# If x ≠ y, is x + y = xy?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 44398
If x ≠ y, is x + y = xy? [#permalink]

### Show Tags

11 Nov 2017, 09:39
Expert's post
1
This post was
BOOKMARKED
00:00

Difficulty:

45% (medium)

Question Stats:

71% (00:55) correct 29% (01:41) wrong based on 41 sessions

### HideShow timer Statistics

If x ≠ y, is x + y = xy?

(1) $$(1 - x)(1 - y) = 1$$

(2) $$x^2 - y^2 = x^2y - xy^2$$
[Reveal] Spoiler: OA

_________________
Math Expert
Joined: 02 Aug 2009
Posts: 5727
Re: If x ≠ y, is x + y = xy? [#permalink]

### Show Tags

11 Nov 2017, 09:59
Bunuel wrote:
If x ≠ y, is x + y = xy?

(1) $$(1 - x)(1 - y) = 1$$

(2) $$x^2 - y^2 = x^2y - xy^2$$

(1) $$(1 - x)(1 - y) = 1$$.
$$-x-y+1+xy=1...........xy=x+y$$
suff

(2) $$x^2 - y^2 = x^2y - xy^2$$.
$$(x-y)(x+y)=xy(x-y)..................(x-y)(x+y-xy)=0$$
so either x=y or xy=x+y
since x ≠ y, xy=x+y
suff

D
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

GMAT online Tutor

Intern
Joined: 02 Oct 2017
Posts: 2
Location: Armenia
Concentration: Economics
GPA: 3.3
WE: Consulting (Consulting)
If x ≠ y, is x + y = xy? [#permalink]

### Show Tags

11 Nov 2017, 10:19
1
This post was
BOOKMARKED
1) 1-y-x+xy=1
xy=1-1+x+y
=> xy=x+y -> sufficient
2)(x-y)(x+y)=xy(x-y)
=> x+y=xy -> sufficient
=> D
If x ≠ y, is x + y = xy?   [#permalink] 11 Nov 2017, 10:19
Display posts from previous: Sort by