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Is x^2 equal to xy?

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Is x^2 equal to xy? [#permalink] New post 20 May 2008, 23:44
00:00
A
B
C
D
E

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  25% (medium)

Question Stats:

69% (02:16) correct 31% (00:51) wrong based on 94 sessions
Is x^2 equal to xy?

(1) x^2 – y^2 = (x + 5)(y - 5)
(2) x = y

OPEN DISCUSSION OF THIS QUESTION IS HERE: is-x-2-equal-to-xy-88034.html
[Reveal] Spoiler: OA

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Last edited by Bunuel on 28 Oct 2014, 03:10, edited 2 times in total.
Edited the question and added the OA.
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Director
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Re: Is x^2 equal to xy? [#permalink] New post 20 May 2008, 23:57
prasannar wrote:
Is x^2 equal to xy?
(1) x2 – y2 = (x + 5)(y - 5)
(2) x = y



D,

1) Assuming x2 - y2 is a typo for x^2-y^2,

(x+y)(x-y) = (-5 + y) (x - (-5) )
i.e. x =-5 & y = -5

2) is suff
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Re: Is x^2 equal to xy? [#permalink] New post 21 May 2008, 00:01
alpha_plus_gamma wrote:
(x+y)(x-y) = (-5 + y) (x - (-5) )
i.e. x =-5 & y = -5


you seem right! :lol:
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Re: Is x^2 equal to xy? [#permalink] New post 21 May 2008, 01:49
Given OA is B.

I too picked D and got nailed down by the OA.

Patman how did you get to B, plz explain
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Re: Is x^2 equal to xy? [#permalink] New post 21 May 2008, 03:34
(1)x^2-y^2=(x+y)(x-y)=(x + 5)(y - 5)
so y=5 but no information abt x so insufficient

(2) x=y
multiplying both sides by x
x^2=xy sufficient
So answer should be B
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Re: Is x^2 equal to xy? [#permalink] New post 21 May 2008, 05:52
this should be B..

x^2-y^2=(x-y)(x+y)..

we have (x+5)(y-5)... (y-5) is not equal to (x-y)

here x is negative...so insuff
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Re: Is x^2 equal to xy? [#permalink] New post 27 Oct 2014, 18:43
prasannar wrote:
Is x^2 equal to xy?
(1) x2 – y2 = (x + 5)(y - 5)
(2) x = y

ritula wrote:
(1)x^2-y^2=(x+y)(x-y)=(x + 5)(y - 5)
so y=5 but no information abt x so insufficient

(2) x=y
multiplying both sides by x
x^2=xy sufficient
So answer should be B

FN wrote:
this should be B..

x^2-y^2=(x-y)(x+y)..

we have (x+5)(y-5)... (y-5) is not equal to (x-y)

here x is negative...so insuff


Can someone please explain this DS problem in more detail?
Bunuel ??... Please can you help! TY :)
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Re: Is x^2 equal to xy? [#permalink] New post 28 Oct 2014, 03:07
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dmmk wrote:
prasannar wrote:
Is x^2 equal to xy?
(1) x2 – y2 = (x + 5)(y - 5)
(2) x = y

ritula wrote:
(1)x^2-y^2=(x+y)(x-y)=(x + 5)(y - 5)
so y=5 but no information abt x so insufficient

(2) x=y
multiplying both sides by x
x^2=xy sufficient
So answer should be B

FN wrote:
this should be B..

x^2-y^2=(x-y)(x+y)..

we have (x+5)(y-5)... (y-5) is not equal to (x-y)

here x is negative...so insuff


Can someone please explain this DS problem in more detail?
Bunuel ??... Please can you help! TY :)


Is x^2 equal to xy?

Question: is \(x^2=xy\)? --> \(x(x-y)=0\) --> Equation holds true if \(x=0\) or/and \(x=y\).

So, basically question asks: Is \(x=0\) or/and \(x=y\) true?

Obviously statement (2) is sufficient, as it gives directly that \(x=y\).

(1) x^2 – y^2 = (x + 5)(y - 5) --> \((x+y)(x-y)=(x + 5)(y-5)\)

If \(y=5\) --> \((x+5)(x-5)=(x+5)(5-5)\) --> \((x+5)(x-5)=0\) --> Either \(x=5=y\) and in this case answer to the question is YES OR \(x=-5\), hence \(x\) is not equal to \(y\) (nor to zero) and in this case answer to the question is NO. So two different answers.

Not sufficient.

Answer: B.

OPEN DISCUSSION OF THIS QUESTION IS HERE: is-x-2-equal-to-xy-88034.html
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Re: Is x^2 equal to xy?   [#permalink] 28 Oct 2014, 03:07
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