Does xy = x^2? 1) xy = y^2 2) x^2 = y^2 : DS Archive
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# Does xy = x^2? 1) xy = y^2 2) x^2 = y^2

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Senior Manager
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Does xy = x^2? 1) xy = y^2 2) x^2 = y^2 [#permalink]

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19 Nov 2005, 16:46
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Does xy = x^2?

1) xy = y^2
2) x^2 = y^2
SVP
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Re: DS: xy = x^2 [#permalink]

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19 Nov 2005, 17:37
A...
from i, x = y. xy = x.x = x^2.
from ii, x = + or -y. xy = x^2 or -x^2.
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Re: DS: xy = x^2 [#permalink]

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19 Nov 2005, 17:53
sudhagar wrote:
Does xy = x^2?

1) xy = y^2
2) x^2 = y^2

xy = x^2 ==> y = x?

1) xy = y^2 ==> x = y. Sufficient.
2) x could be -ve, y could be +ve. Insufficient.
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19 Nov 2005, 18:45
A for me too..
(1) is simple...

(2) though I thought about it..

x=+-y so if x=-y then xy=-y^2 which is not equal to x^2...

and vice versa....

Insuff...
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I go with C [#permalink]

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19 Nov 2005, 19:11
C

from i)
xy=y^2 => xy - y^2 => y(x-y)=0
so either y=0 or x=y
two conditions so insufficient

from ii)
(x - y) (x+y) =0
either x=y or x=-y
so insufficient

so the answer is C
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19 Nov 2005, 19:12
OA is C.

I too choose C in the sample test with the same working as you guys, however the OE mentioned that y could be zero. In that case, x could be any value.
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19 Nov 2005, 20:58
sudhagar wrote:
OA is C.

oh yes, i did not think that y could be 0.
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20 Nov 2005, 06:36
Good one...forgot possibility that y=0 fully...

Rgds
Re   [#permalink] 20 Nov 2005, 06:36
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# Does xy = x^2? 1) xy = y^2 2) x^2 = y^2

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