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

 It is currently 16 Oct 2018, 03:58

### 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

# If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1)

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

### Hide Tags

Senior Manager
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 478
Location: United Kingdom
Concentration: International Business, Strategy
GMAT 1: 730 Q49 V45
GPA: 2.9
WE: Information Technology (Consulting)
If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1)  [#permalink]

### Show Tags

Updated on: 26 Feb 2012, 16:05
2
1
00:00

Difficulty:

25% (medium)

Question Stats:

80% (01:18) correct 20% (01:36) wrong based on 171 sessions

### HideShow timer Statistics

If y^2 = 2, what is the value of $$\frac{2^{(x-y)(x+y)}}{2^{(x-1)(x+1)}}$$?

(A) -2
(B) -1
(C) 1/2
(D) 2
(E) 4

Any idea how to solve?

_________________

Best Regards,
E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730

Originally posted by enigma123 on 26 Feb 2012, 15:40.
Last edited by Bunuel on 26 Feb 2012, 16:05, edited 1 time in total.
Edited the question
Math Expert
Joined: 02 Sep 2009
Posts: 49892
Re: Value question  [#permalink]

### Show Tags

26 Feb 2012, 16:02
enigma123 wrote:
If $$y^2$$ = 2, what is the value of $$\frac{2 (x-y) (x+y)}{2(x-1) (x+1)}$$
(A) -2
(B) -1
(C) $$\frac{1}{2}$$
(D) 2
(E) 4

Any idea how to solve?

From the given OA I think that the question should be as follows:

If y^2 = 2, what is the value of $$\frac{2^{(x-y)(x+y)}}{2^{(x-1)(x+1)}}$$?

Apply $$(a-b)(a+b)=a^2-b^2$$: $$\frac{2^{(x^2-y^2)}}{2^{(x^2-1)}}=2^{(x^2-y^2-(x^2-1))}=2^{(-y^2+1)}=2^{(-2+1)}=2^{(-1)}=\frac{1}{2}$$.

Similar question to practice: gmatprep-special-products-question-107238.html

Hope it helps.
_________________
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3825
Location: United States (CA)
Re: If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1)  [#permalink]

### Show Tags

27 Feb 2017, 12:05
enigma123 wrote:
If y^2 = 2, what is the value of $$\frac{2^{(x-y)(x+y)}}{2^{(x-1)(x+1)}}$$?

(A) -2
(B) -1
(C) 1/2
(D) 2
(E) 4

Let’s first separately simplify the numerator and denominator.

2^[(x-y)(x+y)] = 2^(x^2-y^2)

2^[(x-1)(x+1)] = 2^(x^2-1)

Now we have:

[2^(x^2-y^2)]/[2^(x^2-1)] = 2^[(x^2-y^2) - (x^2-1)] = 2^(-y^2 +1)

Since y^2 = 2, -y^2 = -2, so we have:

2^(-2 +1) = 2^-1 = 1/2.

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1) &nbs [#permalink] 27 Feb 2017, 12:05
Display posts from previous: Sort by

# If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1)

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

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.