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Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|

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Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 29 Sep 2017, 03:57
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

48% (00:46) correct 52% (00:41) wrong based on 119 sessions

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Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post Updated on: 29 Sep 2017, 21:18
1
1
Bunuel wrote:
Is x^3 > 0?

(1) (x + y)(x – y) = 0
(2) x = |y|


The question essentially asks is \(x>0\) i.e. positive

Statement 1: implies \(x=-y\) or \(x=y\). but we don't know what is the sign of \(y\). Hence insufficient

Statement 2: this implies that either \(x\) is positive or \(0\) when \(y=0\). Hence \(x^3\) will either be positive or equal to \(0\). Insufficient.

Combining 1 & 2, again we have either \(x>0\) or \(x=0\). Hence Insufficient

Option E

Originally posted by niks18 on 29 Sep 2017, 04:26.
Last edited by niks18 on 29 Sep 2017, 21:18, edited 1 time in total.
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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 29 Sep 2017, 05:48
2
niks18 wrote:
Bunuel wrote:
Is x^3 > 0?

(1) (x + y)(x – y) = 0
(2) x = |y|


The question essentially asks is \(x>0\) i.e. positive

Statement 1: implies \(x=-y\) or \(x=y\). but we don't know what is the sign of \(y\). Hence insufficient

Statement 2: mod is always positive. hence \(x\) must be positive for \(x=|y|\) to hold true. Hence sufficient

Option B

I think it is wrong. because x can also be 0 in statement 2, which makes the statement insufficient.

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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 29 Sep 2017, 05:48
AlisherChaman wrote:
niks18 wrote:
Bunuel wrote:
Is x^3 > 0?

(1) (x + y)(x – y) = 0
(2) x = |y|


The question essentially asks is \(x>0\) i.e. positive

Statement 1: implies \(x=-y\) or \(x=y\). but we don't know what is the sign of \(y\). Hence insufficient

Statement 2: mod is always positive. hence \(x\) must be positive for \(x=|y|\) to hold true. Hence sufficient

Option B

I think it is wrong. because x can also be 0 in statement 2, which makes the statement insufficient.

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Thus my answer is E

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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 29 Sep 2017, 13:54
AlisherChaman wrote:
niks18 wrote:
Bunuel wrote:
Is x^3 > 0?

(1) (x + y)(x – y) = 0
(2) x = |y|


The question essentially asks is \(x>0\) i.e. positive

Statement 1: implies \(x=-y\) or \(x=y\). but we don't know what is the sign of \(y\). Hence insufficient

Statement 2: mod is always positive. hence \(x\) must be positive for \(x=|y|\) to hold true. Hence sufficient

Option B

I think it is wrong. because x can also be 0 in statement 2, which makes the statement insufficient.

Sent from my SM-J120H using GMAT Club Forum mobile app


Good observation Alisher.

I almost missed that and got dragged by the use of mod.
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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 29 Sep 2017, 21:15
AlisherChaman wrote:
niks18 wrote:
Bunuel wrote:
Is x^3 > 0?

(1) (x + y)(x – y) = 0
(2) x = |y|


The question essentially asks is \(x>0\) i.e. positive

Statement 1: implies \(x=-y\) or \(x=y\). but we don't know what is the sign of \(y\). Hence insufficient

Statement 2: mod is always positive. hence \(x\) must be positive for \(x=|y|\) to hold true. Hence sufficient

Option B

I think it is wrong. because x can also be 0 in statement 2, which makes the statement insufficient.

Sent from my SM-J120H using GMAT Club Forum mobile app


Hi AlisherChaman

Yes agreed absolute value can be zero as x=|y| has a "V" shaped graph and at coordinate (0,0), both (x,y) will be 0. Thanks for pointing it out, I'll make the necessary changes :-)
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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 29 Sep 2017, 23:21
It would be E, if you consider the possibility of zero.
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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y|  [#permalink]

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New post 01 Oct 2017, 03:27
IMO E
1> X = -y OR x = y , we dont know what is y INSUFFICIENT
2> x=|y| , which implies x could be 0 or greater than 0 , but no definite answer

Combine both , no definite answer
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Re: Is x^3 > 0? (1) (x + y)(x – y) = 0 (2) x = |y| &nbs [#permalink] 01 Oct 2017, 03:27
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