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Work Your Abs

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stevenstratmann
 Post subject: Work Your Abs
 Post Posted: Sat Jan 22, 2011 10:46 am 
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Course Students


Posts: 5
What is the value of y?

(1) 3|x^2 – 4| = y – 2

(2) |3 – y| = 11

D.S. question (2) is easy and I understand the outcome is either 14, -8

question (1) I knew the solution could not be obtained from this question alone so I figured (together) you would isolate the absolute value information and set it equal to the other numbers and then another equation setting the numbers within the absolute value equal to the opposite of the other numbers. For instance:

x^2-4 = y-2/3 and the opposite x^2-4 = -y/3 + 2/3

and conclude that one number from stem 2 (14, -8) equals the same value for 'x' and the other does not. This tactic was not the case.

REVIEWING -> the explanation states that x^2-4 is >-0- which makes sense but why would not my attempt or thought process have worked also?

Thanks!
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jnelson0612
 Post subject: Re: Work Your Abs
 Post Posted: Sun Jan 23, 2011 5:30 pm 
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ManhattanGMAT Staff


Posts: 1857
Hi Steven,
The explanation in this thread my help you: absolute-values-t5494.html

Basically, we know that the left side HAS to be positive--there is no way around it. As a result, the right side has to be positive too. You do not need to set up a negative scenario.

Again, check out Emily's explanation in the thread above and let us know if you need further clarification.

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Jamie Nelson
ManhattanGMAT Instructor
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