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Is xy = -1 ?

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sugu86
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Is xy = -1 ? [#permalink] New post   Updated on: 27 May 2014, 00:54
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69% (00:46) correct 31% (00:47) wrong based on 165 sessions
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Is xy = -1 ?

(1) x = y
(2) y= 1
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A

Originally posted by sugu86 on 26 Apr 2012, 02:11.
Last edited by Bunuel on 27 May 2014, 00:54, edited 2 times in total.
Edited the question and added the OA
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Re: Is xy = -1 ? (1) x = y (2) y= 1 [#permalink] New post   26 Apr 2012, 02:19
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Is xy = -1 ?

(1) x = y --> xy=x^2 --> square of a number is always non-negative so xy=x^2 cannot equal to a negative number (-1). The answer to the question is NO. Sufficient.

(2) y= 1. Not sufficient as no info about x.

Answer: A.
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Re: Is xy = -1 ? (1) x = y (2) y= 1 [#permalink] New post   26 Apr 2012, 10:54
Bunuel wrote:
Is xy = -1 ?

(1) x = y --> xy=x^2 --> square of a number is always non-negative so xy=x^2 cannot equal to a negative number (-1). The answer to the question is NO. Sufficient.

(2) y= 1. Not sufficient as no info about x.

Answer: A.


I am sorry, but why cant be x=y=0?

I thought that the answ is C
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Re: Is xy = -1 ? (1) x = y (2) y= 1 [#permalink] New post   26 Apr 2012, 10:57
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LalaB wrote:
Bunuel wrote:
Is xy = -1 ?

(1) x = y --> xy=x^2 --> square of a number is always non-negative so xy=x^2 cannot equal to a negative number (-1). The answer to the question is NO. Sufficient.

(2) y= 1. Not sufficient as no info about x.

Answer: A.


I am sorry, but why cant be x=y=0?

I thought that the answ is C


If for (1) x=y=0 then xy=0 so xy does not equal to -1. So (1) is still sufficient.
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Re: Is xy = -1 ? (1) x = y (2) y= 1 [#permalink] New post   26 Apr 2012, 11:01
Bunuel wrote:

If for (1) x=y=0 then xy=0 so xy does not equal to -1. So (1) is still sufficient.


my mistake.I was careless
thnx
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DS strange question [#permalink] New post   25 May 2014, 04:37
Is XY= -1 ?

a) x=y
b) y=1

I have written this question in my notebook and answer is A, but I don't remember its source now. and this question confuses me now.
If I consider statement (a) x^2=-1 this gives answer according to my notebook. but how ? kindly tell any one
and If some found this question interesting then don't forget to gives kudos :) thanks in advance
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Re: DS strange question [#permalink] New post   25 May 2014, 05:29
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awal_786@hotmail.com wrote:
Is XY= -1 ?

a) x=y
b) y=1

I have written this question in my notebook and answer is A, but I don't remember its source now. and this question confuses me now.
If I consider statement (a) x^2=-1 this gives answer according to my notebook. but how ? kindly tell any one
and If some found this question interesting then don't forget to gives kudos :) thanks in advance


Merging similar topics. Please refer to the discussion above and ask if anything remains unclear.

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Re: Is xy = -1 ? [#permalink] New post   08 Aug 2015, 10:37
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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).

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Re: Is xy = -1 ? [#permalink]
08 Aug 2015, 10:37
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Bunuel
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