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# If denotes a mathematical operation, does x y=y x for all x

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Manager
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If denotes a mathematical operation, does x y=y x for all x [#permalink]  03 May 2008, 12:02
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If ☉ denotes a mathematical operation, does
x☉y=y☉x for all x and y?
(1) For all x and y, x☉y = 2(x^2 + y^2).
(2) For all y, 0☉y = 2 y^2

Last edited by el1981 on 03 May 2008, 17:13, edited 1 time in total.
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Re: DS 5-23 [#permalink]  04 May 2008, 04:38
sondenso wrote:
el1981 wrote:
If ☉ denotes a mathematical operation, does
x☉y=y☉x for all x and y?
(1) For all x and y, x☉y = 2(x^2 + y^2).
(2) For all y, 0☉y = 2 y^2

A

I would take A as well, as B would be a special case of A and doesn't always apply.
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Re: DS 5-23 [#permalink]  04 May 2008, 08:06
1)
x?y=2*(x*x+y*y)
y?x=2*(y*y+x*x)
sufficient

2)
no information is given about x
insufficient

A
Re: DS 5-23   [#permalink] 04 May 2008, 08:06
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