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# What is the value of x^2 − y^2 ?

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Joined: 01 Sep 2010
Posts: 3433
What is the value of x^2 − y^2 ? [#permalink]

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27 Jul 2017, 08:09
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Difficulty:

25% (medium)

Question Stats:

68% (00:55) correct 32% (01:04) wrong based on 242 sessions

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

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

(2) x + y = 6

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Math Expert
Joined: 02 Aug 2009
Posts: 6233
Re: What is the value of x^2 − y^2 ? [#permalink]

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27 Jul 2017, 09:14
1
1
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
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Posts: 343
Re: What is the value of x^2 − y^2 ? [#permalink]

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06 Aug 2017, 07:50
1
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, 07:50
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