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M9 #21

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Joined: 11 Jun 2007
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M9 #21 [#permalink]

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New post 21 Sep 2009, 00:51
If the operation \(#\) satisfies \(X#Y = \frac{1}{X#Y}\) for any non-zero number \(X\) and \(Y\) , which of the following can be \(#\) ?

1. \(X#Y = \frac{1}{XY}\)
2. \(X#Y = \frac{X}{Y}\)
3. \(X#Y = XY\)

I understood the answer how X#Y can only be 1 or -1 but can someone explain why 1, 2, or 3 could not equal 1 or -1. Thanks.

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Re: M9 #21 [#permalink]

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New post 28 Sep 2009, 12:15
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Can you post the entire question.

1. 1/XY=XY
2. X/Y = Y/X
3. XY = 1/XY (same as No. 1)

These are the 3 condition. Now for condition 2. X & Y does not have to be just 1 or -1 it can be any integer as long as X=Y
for example X=2 Y=2 -> X/Y is Y/X

but for 1 & 3 X & Y can be only 1 or -1.
you should also take fraction since it does not say integer.

What are the answer choices?

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Concentration: Technology, Other
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Re: M9 #21 [#permalink]

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New post 01 Jun 2014, 05:24
If the operation # satisfies X # Y = 1/(X # Y) for any non-zero number X and Y, which of the following can be #?

1. X # Y = 1/XY
2. X # Y = X/Y
3. X # Y = XY

None
1 only
2 only
1 and 2 only
1 and 3 only

I still cannot figure this question out , can anyone help me out here ?

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Re: M9 #21 [#permalink]

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New post 01 Jun 2014, 05:37
shelrod007 wrote:
If the operation # satisfies X # Y = 1/(X # Y) for any non-zero number X and Y, which of the following can be #?

1. X # Y = 1/XY
2. X # Y = X/Y
3. X # Y = XY

None
1 only
2 only
1 and 2 only
1 and 3 only

I still cannot figure this question out , can anyone help me out here ?


This question was removed from data base. So, don't worry about it.
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Re: M9 #21   [#permalink] 01 Jun 2014, 05:37
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