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# S is a set of integers such that I) If x is in S, then –x is

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S is a set of integers such that I) If x is in S, then –x is [#permalink]  25 Apr 2012, 21:58
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S is a set of integers such that
I) If x is in S, then –x is in S.
II) If both x and y are in S, then so is x + y.
Is –2 in S?

(1) 1 is in S.
(2) 0 is in S.

[Reveal] Spoiler:
A
, but i didnot find the explanation given in the book convincing.Please help. I thought the ans. to be E.
[Reveal] Spoiler: OA

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Last edited by Bunuel on 25 Apr 2012, 22:16, edited 1 time in total.
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Re: S is a set of integers such that I) If x is in S, then –x is [#permalink]  25 Apr 2012, 22:27
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conty911 wrote:
S is a set of integers such that
I) If x is in S, then –x is in S.
II) If both x and y are in S, then so is x + y.
Is –2 in S?

(1) 1 is in S.
(2) 0 is in S.

[Reveal] Spoiler:
A
, but i didnot find the explanation given in the book convincing.Please help. I thought the ans. to be E.

You are right answer should be E, not A.

S is a set of integers such that
I) If x is in S, then –x is in S.
II) If both x and y are in S, then so is x + y.
Is –2 in S?

(1) 1 is in S --> according to (I) -1 is also in S. Next, according to (II) -1+1=0 also in S. We don't know whether -2 is in the set, for example S could be {-1, 0, 1}. Not sufficient.

(2) 0 is in S. Not sufficient.

(1)+(2) Nothing new. Not sufficient.

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k-is-a-set-of-numbers-such-that-i-if-x-is-in-k-then-x-96907.html
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s-is-a-set-of-integers-such-that-i-if-a-is-in-s-then-a-130000.html

Hope it helps.
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Re: S is a set of integers such that I) If x is in S, then –x is [#permalink]  25 Apr 2012, 23:19
Thankyou, it really helped me in resolving my confusion .The explanation given in the book for statement 1 was -1+(-1)=-2 rather than 1-1=0;so they must have assumed x=y;
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Re: S is a set of integers such that I) If x is in S, then –x is [#permalink]  28 Apr 2012, 15:48
IMO very bad question .... they have not clearly stated the domain conditions. Kindly use the good materials only.
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Re: S is a set of integers such that I) If x is in S, then –x is   [#permalink] 28 Apr 2012, 15:48
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