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# Is x^2 equal to xy? (1) x^2 y^2 = (x + 5)(y - 5) (2) x = y

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Senior Manager
Joined: 02 Dec 2007
Posts: 422
Is x^2 equal to xy? (1) x^2 y^2 = (x + 5)(y - 5) (2) x = y [#permalink]

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21 Oct 2008, 09:41
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Is x^2 equal to xy?
(1) x^2 – y^2 = (x + 5)(y - 5)
(2) x = y

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

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Retired Moderator
Joined: 05 Jul 2006
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21 Oct 2008, 11:00
Is x^2 equal to xy?
(1) x^2 – y^2 = (x + 5)(y - 5)
(2) x = y

1) (x-y)(x+y) = (x -(- 5)) (-5+Y).........x = y = -5........suff

2) suff

D
Senior Manager
Joined: 02 Dec 2007
Posts: 422

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21 Oct 2008, 11:04
OA is B however I dont agree with it.
Retired Moderator
Joined: 18 Jul 2008
Posts: 898

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21 Oct 2008, 11:21
It does not say x^2-y^2 = (x + 5)(y - 5) = 0

Therefore you can't say x = 5, y = -5.

yezz wrote:
Is x^2 equal to xy?
(1) x^2 – y^2 = (x + 5)(y - 5)
(2) x = y

1) (x-y)(x+y) = (x -(- 5)) (-5+Y).........x = y = -5........suff

2) suff

D
Senior Manager
Joined: 02 Dec 2007
Posts: 422

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21 Oct 2008, 12:53
Guys do you think we can assume X^2 - Y ^2 = (X+Y)(X-Y) in (1)
Manager
Joined: 15 Oct 2008
Posts: 102

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22 Oct 2008, 11:33
Nihit wrote:
Guys do you think we can assume X^2 - Y ^2 = (X+Y)(X-Y) in (1)

It is always right to have X^2 - Y^2 = (x+y) (x-Y)
It is not something we have to assume
However, we cannot assume that X^2 - Y^2 = (x+y) (x-Y) = 0

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: DS x& y   [#permalink] 22 Oct 2008, 11:33
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