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Does the product of A and B equal to 1 ? 1) A*B*A = A 2)

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Senior Manager
Joined: 11 May 2006
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Does the product of A and B equal to 1 ? 1) A*B*A = A 2) [#permalink]

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23 Sep 2006, 09:26
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Does the product of A and B equal to 1 ?

1) A*B*A = A
2) B*A*B = B
VP
Joined: 02 Jun 2006
Posts: 1261
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Kudos [?]: 87 [0], given: 0

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23 Sep 2006, 09:43

S1. A^2B - A = 0

or A(AB-1) = 0

A = 0 OR AB = 1

If A = 0, then AB = 0
If AB=1, then AB = 1

Not sufficient.

S2: B^2A -B =0
B(AB-1) = 0

B=0, OR AB =1

If B=0, then AB=0
If AB=1, then AB=1
Not sufficient.

S1 & S2:
A =0 OR B=0 OR AB=1

If A=0 or B=0, then AB=0
If AB=1, then AB=1

Not sufficient.

SVP
Joined: 01 May 2006
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23 Sep 2006, 09:44
(E)

We have the case A=B=0 that remains, along with A=B=1.
SVP
Joined: 05 Jul 2006
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23 Sep 2006, 10:37
Does the product of A and B equal to 1 ?

1) A*B*A = A
2) B*A*B = B

FOR THE PRODUCT OF A,B TO EQUAL ONE

A=B=-1 OR A=B=1 OR THEY ARE RECEPROCALS

FROM ONE

A,B =1OR -1 OR A,B = ZERO.....INSUFF

FROM TWO

A,B = 1 OR -1 OR A,B = ZERO.....INSUFF

BOTH TOGETHER are insuff...my answer is E
Senior Manager
Joined: 11 Jul 2006
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Location: TX
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23 Sep 2006, 19:17
Guys I am amazed at the speed all of you answer questions . Great going ...

Yup I got E too.
23 Sep 2006, 19:17
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