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Advanced Gmat Quant - Chapter 4 Qn 12

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huiting
 Post subject: Advanced Gmat Quant - Chapter 4 Qn 12
 Post Posted: Wed Nov 02, 2011 12:21 am 
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Students


Posts: 2
What is the value of |x+4|?

1) x^2 + 8x + 12=0

2) x^2 + 6x = 0

The correct answer for this Questions is A. What I don't get is why is the answer not D since one of the solutions from Statement 2 also leads you to x= -6.
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sunil.kapil1277
 Post subject: Re: Advanced Gmat Quant - Chapter 4 Qn 12
 Post Posted: Thu Nov 03, 2011 11:41 am 
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Posts: 2
as per statement 1, x can take two values , i.e. -2 & -6.

on putting both the value in mod(x+4), we get 2 as an answer.
as we can get a unique answer for the question, statement is sufficient

as per statement 2, x can take two values, i.e. 0 & -6.

on putting x as 0 in mod(x+4), we get 4 as an answer
on putting x as -6 in mod(x+4), we get 2 as an answer
therefore statement 2 is not sufficient to determine the value of mod(x+4)

hence, the answer A..
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jnelson0612
 Post subject: Re: Advanced Gmat Quant - Chapter 4 Qn 12
 Post Posted: Mon Nov 14, 2011 12:03 am 
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ManhattanGMAT Staff


Posts: 1857
Thanks Sunil!

Hulting, check out how you can factor statement 2:

x^2 + 6x=0. Factor out an x.

x(x+6)=0

We must set "x" and "x+6" equal to zero; thus, x could be 0 or -6. Please write back if you need more assistance. :-)

_________________
Jamie Nelson
ManhattanGMAT Instructor
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