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What is the value of x ?

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Senior Manager
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Joined: 10 Apr 2012
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Kudos [?]: 139 [0], given: 323

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What is the value of x ? [#permalink] New post 11 Feb 2013, 00:09
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Difficulty:

  35% (medium)

Question Stats:

60% (01:47) correct 40% (00:38) wrong based on 43 sessions
What is the value of x ?

(1) x^4=|x|
(2) x^2>x

M22-03

please explain ..

thanks in advance
[Reveal] Spoiler: OA
Expert Post
1 KUDOS received
Math Expert
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Joined: 02 Sep 2009
Posts: 23064
Followers: 3537

Kudos [?]: 27224 [1] , given: 2725

Re: What is the value of x ? [#permalink] New post 11 Feb 2013, 00:18
1
This post received
KUDOS
Expert's post
guerrero25 wrote:
What is the value of x ?

(1) x^4=|x|
(2) x^2>x

M22-03

please explain ..

thanks in advance


What is the value of x ?

(1) x^4 = |x|. Square both sides: x^8=x^2 --> x^2(x^6-1)=0 --> x^2(x^3-1)(x^3+1)=0 --> x=-1, x=0, or x=1. Not sufficient.

(2) x^2> x. Rearrange and factor out x to get x(x-1)>0. The roots are x=0 and x=1, ">" sign means that the given inequality holds true for: x<0 and x>1 (check here: x2-4x-94661.html#p731476, inequalities-trick-91482.html, everything-is-less-than-zero-108884.html?hilit=extreme#p868863, xy-plane-71492.html?hilit=solving%20quadratic#p841486). Not sufficient.

(1)+(2) The only value of x from (1) which is in the range from (2) is x=-1. Sufficient.

Answer: C.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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.


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Senior Manager
Senior Manager
avatar
Joined: 10 Apr 2012
Posts: 279
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE: Project Management (Telecommunications)
Followers: 2

Kudos [?]: 139 [0], given: 323

GMAT ToolKit User Premium Member CAT Tests
Re: What is the value of x ? [#permalink] New post 12 Feb 2013, 03:04
Bunuel wrote:
guerrero25 wrote:
What is the value of x ?

(1) x^4=|x|
(2) x^2>x

M22-03

please explain ..

thanks in advance


What is the value of x ?

(1) x^4 = |x|. Square both sides: x^8=x^2 --> x^2(x^6-1)=0 --> x^2(x^3-1)(x^3+1)=0 --> x=-1, x=0, or x=1. Not sufficient.

(2) x^2> x. Rearrange and factor out x to get x(x-1)>0. The roots are x=0 and x=1, ">" sign means that the given inequality holds true for: x<0 and x>1 (check here: x2-4x-94661.html#p731476, inequalities-trick-91482.html, everything-is-less-than-zero-108884.html?hilit=extreme#p868863, xy-plane-71492.html?hilit=solving%20quadratic#p841486). Not sufficient.

(1)+(2) The only value of x from (1) which is in the range from (2) is x=-1. Sufficient.

Answer: C.


Thanks for the crystal clear approach .. Could you help me with a link here to grasp the concept on Absolute value type questions . I still get problems related to them wrong . Appreciate your help .

thanks again!
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23064
Followers: 3537

Kudos [?]: 27224 [1] , given: 2725

Re: What is the value of x ? [#permalink] New post 12 Feb 2013, 04:33
1
This post received
KUDOS
Expert's post
guerrero25 wrote:
Bunuel wrote:
guerrero25 wrote:
What is the value of x ?

(1) x^4=|x|
(2) x^2>x

M22-03

please explain ..

thanks in advance


What is the value of x ?

(1) x^4 = |x|. Square both sides: x^8=x^2 --> x^2(x^6-1)=0 --> x^2(x^3-1)(x^3+1)=0 --> x=-1, x=0, or x=1. Not sufficient.

(2) x^2> x. Rearrange and factor out x to get x(x-1)>0. The roots are x=0 and x=1, ">" sign means that the given inequality holds true for: x<0 and x>1 (check here: x2-4x-94661.html#p731476, inequalities-trick-91482.html, everything-is-less-than-zero-108884.html?hilit=extreme#p868863, xy-plane-71492.html?hilit=solving%20quadratic#p841486). Not sufficient.

(1)+(2) The only value of x from (1) which is in the range from (2) is x=-1. Sufficient.

Answer: C.


Thanks for the crystal clear approach .. Could you help me with a link here to grasp the concept on Absolute value type questions . I still get problems related to them wrong . Appreciate your help .

thanks again!


Theory on Absolute Values: math-absolute-value-modulus-86462.html

PS questions on Absolute Values: search.php?search_id=tag&tag_id=58
DS questions on Absolute Values: search.php?search_id=tag&tag_id=37

Tough inequality and absolute value questions: inequality-and-absolute-value-questions-from-my-collection-86939.html

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Senior Manager
Senior Manager
avatar
Joined: 10 Apr 2012
Posts: 279
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE: Project Management (Telecommunications)
Followers: 2

Kudos [?]: 139 [0], given: 323

GMAT ToolKit User Premium Member CAT Tests
Re: What is the value of x ? [#permalink] New post 12 Feb 2013, 06:14
Hope it helps.[/quote]

Thanks GMATCLUB is my Bible
Re: What is the value of x ?   [#permalink] 12 Feb 2013, 06:14
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