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Is |x| = |y|? (1) x = -y (2) x^2 = y^2

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Joined: 18 Feb 2015
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Is |x| = |y|? (1) x = -y (2) x^2 = y^2 [#permalink]

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16 Dec 2015, 07:06
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Is |x| = |y|?

(1) x = -y
(2) x^2 = y^2

[Reveal] Spoiler:
I found this question in GMAT Prep and selected ST2 as the answer but that's wrong.

Normally, x^2 would equal to lxl since it will contain both signs "positive as well as negative". How come st 1 is true?

Does it assume that since +x = -y, it must be true that -x is also equal to -y or?

What am I missing?

[Reveal] Spoiler: OA

Last edited by Bunuel on 11 Nov 2017, 01:25, edited 3 times in total.
Formatted the question.

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Current Student
Joined: 20 Mar 2014
Posts: 2676

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Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
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WE: Engineering (Aerospace and Defense)
Re: Is |x| = |y|? (1) x = -y (2) x^2 = y^2 [#permalink]

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16 Dec 2015, 07:38
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HarveyKlaus wrote:
Is lxl = lyl ?

A) x=-y
b) x^2 = y^2

[Reveal] Spoiler:
I found this question in GMAT Prep and selected ST2 as the answer but that's wrong.

Normally, x^2 would equal to lxl since it will contain both signs "positive as well as negative". How come st 1 is true?

Does it assume that since +x = -y, it must be true that -x is also equal to -y or?

What am I missing?

You are asked whether |x|=|y| or in other words, is the distance of x from 0 = distance of y from 0 ? You would get a yes if x= y or x=-y. Lets evaluate the choices.

Per statement 1:$$x=-y$$ . Clearly this is one of the conditions we are looking for. Assume 2-3 different values. x=2, y = -2 --> 2 and -2 are both 2 units from 0 . Similar for 3/-3 or 10/-10 etc. Thus this statement is sufficient.

Per statement 2: $$x^2=y^2$$ ---> $$x= \pm y$$. Again both the cases, x=y and x=-y give you a "yes" for the question asked as is hence sufficient.

Both statements are sufficient ---> D is the correct answer.

Kudos [?]: 1775 [1], given: 794

Senior Manager
Joined: 20 Feb 2015
Posts: 388

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Concentration: Strategy, General Management
Re: Is |x| = |y|? (1) x = -y (2) x^2 = y^2 [#permalink]

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17 Dec 2015, 06:54
statement 1 is sufficient as absolute value for -ve should give +ve
statement 2 is sufficient as
it will give either x and y both are +ve or both are -ve

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Intern
Joined: 15 Sep 2017
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Re: Is |x| = |y|? (1) x = -y (2) x^2 = y^2 [#permalink]

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10 Nov 2017, 15:24
Is |x|=|y|?

1) x=-y

2) x^2=y^2

Kudos [?]: 0 [0], given: 23

Manager
Joined: 15 Feb 2017
Posts: 71

Kudos [?]: 58 [3], given: 0

Re: Is |x| = |y|? (1) x = -y (2) x^2 = y^2 [#permalink]

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10 Nov 2017, 17:20
3
KUDOS
You are asked whether |x|=|y| or in other words, is the distance of x from 0 = distance of y from 0 ? You would get a yes if x= y or x=-y. Lets evaluate the choices.

Per statement 1:x=−yx=−y . Clearly this is one of the conditions we are looking for. Assume 2-3 different values. x=2, y = -2 --> 2 and -2 are both 2 units from 0 . Similar for 3/-3 or 10/-10 etc. Thus this statement is sufficient.

Per statement 2: x2=y2x2=y2 ---> x=±yx=±y. Again both the cases, x=y and x=-y give you a "yes" for the question asked as is hence sufficient.

Both statements are sufficient ---> D is the correct answer.
Please give me kudos. I need them to unlock gmatclub tests.

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Joined: 02 Sep 2009
Posts: 42326

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Re: Is |x| = |y|? (1) x = -y (2) x^2 = y^2 [#permalink]

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11 Nov 2017, 01:25
SamDGold wrote:
Is |x|=|y|?

1) x=-y

2) x^2=y^2

Merging topics. Please check the discussion above.
_________________

Kudos [?]: 133106 [0], given: 12411

Re: Is |x| = |y|? (1) x = -y (2) x^2 = y^2   [#permalink] 11 Nov 2017, 01:25
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