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primes and divisibility 1

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primes and divisibility 1

by Gurpinder » Wed Aug 11, 2010 8:13 am
K is a set of number such that

(i) if x is in K, then -x is in K and
(ii) if each of x and y is in K, then xy is in K

Is 12 in K?

(1) 2 is in K
(2) 3 is in k


I got the right answer, but im unsure of whether I the way I got it is right. Please explain this one.
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
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by selango » Wed Aug 11, 2010 8:28 am
stmt1,

2 is in k.So -2 is in k.

-4 also is in k.

We don't abt other values.

Insuff

3 is in k.So -3 is in k.

-9 also is in k

We don't abt other values.

Insuff

Combining 1 and 2,

-3 and -4 are in k.So 12 is in k

Suff

Pick C
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by Gurpinder » Wed Aug 11, 2010 8:34 am
selango wrote:stmt1,

2 is in k.So -2 is in k.

-4 also is in k.

We don't abt other values.

Insuff

3 is in k.So -3 is in k.

-9 also is in k

We don't abt other values.

Insuff

Combining 1 and 2,

-3 and -4 are in k.So 12 is in k

Suff

Pick C
ahh....i get it thx
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
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