It is currently 22 Feb 2018, 17:00

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

Author Message
TAGS:

### Hide Tags

Director
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 527
Location: United Kingdom
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

26 Feb 2012, 14:40
2
KUDOS
1
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

72% (01:01) correct 28% (01:21) wrong based on 165 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?
[Reveal] Spoiler: OA

_________________

Best Regards,
E.

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

Last edited by Bunuel on 26 Feb 2012, 15:05, edited 1 time in total.
Edited the question
Math Expert
Joined: 02 Sep 2009
Posts: 43867

### Show Tags

26 Feb 2012, 15:02
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.
_________________
Non-Human User
Joined: 09 Sep 2013
Posts: 13804
Re: If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1) [#permalink]

### Show Tags

28 Jan 2014, 15:23
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.
_________________
Non-Human User
Joined: 09 Sep 2013
Posts: 13804
Re: If y^2 = 2, what is the value of 2^(x-y)(x+y)/2^(x-1)(x+1) [#permalink]

### Show Tags

24 Feb 2017, 00:58
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.
_________________
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 2192
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, 11:05
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)   [#permalink] 27 Feb 2017, 11:05
Display posts from previous: Sort by