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# Does x + y = 0? (1) xy<0 (2) x^2 = y^2

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Manager
Joined: 04 Dec 2008
Posts: 111
Followers: 1

Kudos [?]: 59 [0], given: 2

Does x + y = 0? (1) xy<0 (2) x^2 = y^2 [#permalink]  28 Apr 2009, 04:52
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Does x + y = 0?
(1) xy<0
(2) x^2 = y^2

My answer is different from OA. Can someone explain the logic. Will reveal OA later.
Manager
Joined: 12 Apr 2006
Posts: 220
Location: India
Followers: 1

Kudos [?]: 22 [0], given: 17

Re: DS1000 Sec3 #19 [#permalink]  28 Apr 2009, 05:52
Is the OA is C?

This is what I am thinking

1) xy<0 will be true if only one of x or y is -VE. But this didn't answer the ques becuase it can be anything such as x=6 and y=-9, so insufficient

2) x^2 = y^2 will be true for |x|=|y| and for x=y=0. again insufficient

Using both proves one of them is negative and are of same value which is sufficient to answer

x+y=0 as yes

joyseychow wrote:
Does x + y = 0?
(1) xy<0
(2) x^2 = y^2

My answer is different from OA. Can someone explain the logic. Will reveal OA later.
Manager
Joined: 24 May 2007
Posts: 95
Location: Phoenix, AZ
Schools: Stanford R1(W/o Int), HBS R1(W/o Int), Kellogg R1(Ding), Haas R2(W/o Int), Wharton R2(W/o Int), Darden(W/o Int)
Followers: 2

Kudos [?]: 11 [0], given: 5

Re: DS1000 Sec3 #19 [#permalink]  28 Apr 2009, 09:14
C seems like the right answer to me too.
Manager
Joined: 11 Apr 2009
Posts: 169
Followers: 2

Kudos [?]: 27 [0], given: 5

Re: DS1000 Sec3 #19 [#permalink]  28 Apr 2009, 14:29
Me too. I think it's C. Whats the confirmed answer for this?
Senior Manager
Joined: 19 Aug 2006
Posts: 251
Followers: 2

Kudos [?]: 6 [0], given: 0

Re: DS1000 Sec3 #19 [#permalink]  28 Apr 2009, 16:43
IMO C.

stmnt1 - proves that the signs for x and y are different
stmnt2 - nsf, could be 0=0, -1^2=1^2, 1^2=1^2, etc.

if we combine, it's clear it's sufficient
Manager
Joined: 04 Dec 2008
Posts: 111
Followers: 1

Kudos [?]: 59 [0], given: 2

Re: DS1000 Sec3 #19 [#permalink]  04 May 2009, 05:48
humans wrote:
Is the OA is C?

This is what I am thinking

1) xy<0 will be true if only one of x or y is -VE. But this didn't answer the ques becuase it can be anything such as x=6 and y=-9, so insufficient

2) x^2 = y^2 will be true for |x|=|y| and for x=y=0. again insufficient

Using both proves one of them is negative and are of same value which is sufficient to answer

x+y=0 as yes

joyseychow wrote:
Does x + y = 0?
(1) xy<0
(2) x^2 = y^2

My answer is different from OA. Can someone explain the logic. Will reveal OA later.

OA is indeed C. After attempting the ques again, I finally understood why is C strange....
Re: DS1000 Sec3 #19   [#permalink] 04 May 2009, 05:48
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