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If x^2 = y^2, is true that x>0?

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Joined: 31 Jul 2017
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Re: If x^2 = y^2, is true that x>0? [#permalink]

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New post 19 Nov 2017, 17:21
burnttwinky wrote:
If x^2 = y^2, is true that x>0?

(1) x=2y+1

(2) y<= -1


Hi Bunuel, VeritasPrepKarishma

Can you please let me know if my below approach is wrong.

Given, (x+y)(x-y) = 0

1. x - y = y + 1
(x+y)(y+1)=0
So, x = -y or y = -1

2. y <= -1

combining 1 + 2, we get

y = -1, x =-1
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Re: If x^2 = y^2, is true that x>0? [#permalink]

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New post 19 Nov 2017, 22:19
rahul16singh28 wrote:
burnttwinky wrote:
If x^2 = y^2, is true that x>0?

(1) x=2y+1

(2) y<= -1


Hi Bunuel, VeritasPrepKarishma

Can you please let me know if my below approach is wrong.

Given, (x+y)(x-y) = 0

1. x - y = y + 1
(x+y)(y+1)=0
So, x = -y or y = -1


2. y <= -1

combining 1 + 2, we get

y = -1, x =-1


The question asks whether x > 0. It's not clear how you got that (1) is not sufficient.
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Joined: 31 Jul 2017
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Re: If x^2 = y^2, is true that x>0? [#permalink]

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New post 19 Nov 2017, 22:27
Bunuel wrote:
rahul16singh28 wrote:
burnttwinky wrote:
If x^2 = y^2, is true that x>0?

(1) x=2y+1

(2) y<= -1


Hi Bunuel, VeritasPrepKarishma

Can you please let me know if my below approach is wrong.

Given, (x+y)(x-y) = 0

1. x - y = y + 1
(x+y)(y+1)=0
So, x = -y or y = -1


2. y <= -1

combining 1 + 2, we get

y = -1, x =-1


The question asks whether x > 0. It's not clear how you got that (1) is not sufficient.


Hi Bunuel,

Given is (x+y)(x-y)=0 and From Statement 1, x-y = y +1
So substituting x - y = y+1 in above eqn. we get (x+y)(y+1)=0
So, X=-Y or Y = -1
May I please know if anything wrong with above approach??
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Math Expert
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Joined: 02 Sep 2009
Posts: 43363
If x^2 = y^2, is true that x>0? [#permalink]

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New post 19 Nov 2017, 22:30
rahul16singh28 wrote:
Hi Bunuel,

Given is (x+y)(x-y)=0 and From Statement 1, x-y = y +1
So substituting x - y = y+1 in above eqn. we get (x+y)(y+1)=0
So, X=-Y or Y = -1
May I please know if anything wrong with above approach??


Again, how does x = -y or y = -1 give both an YES and a NO answer to the question whether x > 0?
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Manager
Manager
avatar
B
Joined: 31 Jul 2017
Posts: 142
Location: Malaysia
WE: Consulting (Energy and Utilities)
If x^2 = y^2, is true that x>0? [#permalink]

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New post 19 Nov 2017, 22:37
Bunuel wrote:
[quote="rahul16singh28"
Hi Bunuel,

Given is (x+y)(x-y)=0 and From Statement 1, x-y = y +1
So substituting x - y = y+1 in above eqn. we get (x+y)(y+1)=0
So, X=-Y or Y = -1
May I please know if anything wrong with above approach??



Thanks.. Got it :-)
If x^2 = y^2, is true that x>0?   [#permalink] 19 Nov 2017, 22:37

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