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M28#37

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Intern
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Joined: 02 Feb 2013
Posts: 29
Location: India
Concentration: Operations, General Management
GMAT 1: 690 Q47 V38
GMAT 2: 720 Q48 V41
GPA: 3.2
WE: Programming (Computer Software)
Followers: 1

Kudos [?]: 6 [0], given: 18

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M28#37 [#permalink] New post 10 Jul 2013, 04:42
If x is not equal to 0 and xy=1, then which of the following must be true?
I. x=1
II. x=1 and y=0
III. x=1 or y=0

I only
II only
III only
I and III only
None


Notice that if x=−1 and y is any even number, then (−1)even=1, thus none of the options must be true.
The correct answer is E


option C seems to make perfect sense here though. Could someone please elaborate on this please ?
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Re: M28#37 [#permalink] New post 10 Jul 2013, 05:20
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Expert's post
abilash10 wrote:
If x is not equal to 0 and xy=1, then which of the following must be true?
I. x=1
II. x=1 and y=0
III. x=1 or y=0

I only
II only
III only
I and III only
None


Notice that if x=−1 and y is any even number, then (−1)even=1, thus none of the options must be true.
The correct answer is E


option C seems to make perfect sense here though. Could someone please elaborate on this please ?


If x is not equal to 0 and x^y=1, then which of the following must be true?

I. x=1
II. x=1 and y=0
III. x=1 or y=0


A. I only
B. II only
C. III only
D. I and III only
E. None

Notice that if x=-1 and y is any even number, then (-1)^{even}=1, thus none of the options must be true.

Answer: E.

As for your doubt:

Option C is III only: x=1 or y=0. Now, if x=-1 and y=2 (x^y=(-1)^2=1), then neither x is 1 not y is 0, thus this option is not necessarily true.

Hope it's clear.
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Intern
Intern
avatar
Joined: 02 Feb 2013
Posts: 29
Location: India
Concentration: Operations, General Management
GMAT 1: 690 Q47 V38
GMAT 2: 720 Q48 V41
GPA: 3.2
WE: Programming (Computer Software)
Followers: 1

Kudos [?]: 6 [0], given: 18

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Re: M28#37 [#permalink] New post 18 Jul 2013, 19:34
makes sense. Thanks !
Re: M28#37   [#permalink] 18 Jul 2013, 19:34
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M28#37

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