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# What is the value of x^2 − y^2 ?

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Joined: 01 Sep 2010
Posts: 3483
What is the value of x^2 − y^2 ? [#permalink]

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27 Jul 2017, 07:09
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KUDOS
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25% (medium)

Question Stats:

68% (00:57) correct 32% (01:04) wrong based on 188 sessions

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What is the value of $$x^2 - y^2$$ ?

(1) $$(x - y)^2 = 9$$

(2) x + y = 6
[Reveal] Spoiler: OA

_________________
Math Expert
Joined: 02 Aug 2009
Posts: 5662
Re: What is the value of x^2 − y^2 ? [#permalink]

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27 Jul 2017, 08:14
1
KUDOS
Expert's post
carcass wrote:
What is the value of $$x^2 - y^2$$ ?

(1) $$(x - y)^2 = 9$$

(2) x + y = 6

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

STATEMENTS..

(1) $$(x - y)^2 = 9$$
x-y= 3..
x-y=-3..
various combinations of x and y possible fitting in any of two above
insuff

(2) x + y = 6
we do not know what is x-y
insuff

combined..
we know x+y=6..
but x-y can be 3, then ans is 18
OR x-y can be -3 ans will be -18

insuff

E
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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

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Re: What is the value of x^2 − y^2 ? [#permalink]

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06 Aug 2017, 06:50
1
KUDOS
lets consider both case 1 and 2

x=6-y

(6-y-y)^2=9
6-2y=3 or -3
we can have two values of y and x

so, not sufficient

e
Re: What is the value of x^2 − y^2 ?   [#permalink] 06 Aug 2017, 06:50
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