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# M28#37

Author Message
Current Student
Joined: 02 Feb 2013
Posts: 42
Location: India
Concentration: Operations, Technology
GMAT 1: 690 Q47 V38
GMAT 2: 720 Q48 V41
GPA: 3.2
WE: Programming (Computer Software)
Followers: 3

Kudos [?]: 11 [0], given: 20

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10 Jul 2013, 05:42
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.

option C seems to make perfect sense here though. Could someone please elaborate on this please ?
Math Expert
Joined: 02 Sep 2009
Posts: 34449
Followers: 6267

Kudos [?]: 79545 [1] , given: 10022

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10 Jul 2013, 06:20
1
KUDOS
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.

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.

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.
_________________
Current Student
Joined: 02 Feb 2013
Posts: 42
Location: India
Concentration: Operations, Technology
GMAT 1: 690 Q47 V38
GMAT 2: 720 Q48 V41
GPA: 3.2
WE: Programming (Computer Software)
Followers: 3

Kudos [?]: 11 [0], given: 20

### Show Tags

18 Jul 2013, 20:34
makes sense. Thanks !
Re: M28#37   [#permalink] 18 Jul 2013, 20:34
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# M28#37

Moderator: Bunuel

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