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# If x, y, and z are positive integers, is x - y odd? 1. x =

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Manager
Joined: 12 Feb 2006
Posts: 115
If x, y, and z are positive integers, is x - y odd? 1. x = [#permalink]

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28 Feb 2007, 03:06
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If x, y, and z are positive integers, is x - y odd?

1. x = z^2
2. y = (z - 1)^2
SVP
Joined: 01 May 2006
Posts: 1796

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28 Feb 2007, 03:18
(C) for me

x - y odd?

From1
x = z^2

We have no information about y...

INSUFF.

From2
y = (z - 1)^2

We have no information about x...

INSUFF.

both 1 and 2
x-y
= z^2 - (z - 1)^2
= z^2 - (z^2 - 2*z +1)
= 2*z - 1

That is a definition of an odd integer.

SUFF.
Manager
Joined: 04 Oct 2006
Posts: 188

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28 Feb 2007, 06:38
I get C as well. Definitely not A or B since neither one says anything about both X and Y. But the algebra posted definitely agrees with C.
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28 Feb 2007, 06:38
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