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by CSASHISHPANDAY » Sat Jun 29, 2013 11:18 pm
What is the value of y?

(1) 3|x^2 - 4| = y - 2

(2) |3 - y| = 11

Ans C

Somehow I can reach on right ans but want to know that in choice (1) how one can say that

absolute value expression |x^2 - 4| must be greater than or equal to 0.
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Source: — Data Sufficiency |

by GMATGuruNY » Sun Jun 30, 2013 2:17 am
CSASHISHPANDAY wrote:What is the value of y?

(1) 3|x^2 - 4| = y - 2

(2) |3 - y| = 11

Ans C

Somehow I can reach on right ans but want to know that in choice (1) how one can say that

absolute value expression |x^2 - 4| must be greater than or equal to 0.
|a-b| = the DISTANCE between a and b.
Thus, |x²-4| = the distance between x² and 4.
The distance between two values must be NONNEGATIVE.
Thus, |x²-4| ≥ 0.

Statement 1: 3|x^2 - 4| = y - 2

|x²-4| = (y-2)/3.
Since |x²-4| ≥ 0, it must also be true that (y-2)/3 ≥ 0.
Thus:
(y-2)/3 ≥ 0
y-2 ≥ 0
y ≥ 2.
No way to determine the value of y.
INSUFFICIENT.

Statement 2: |3 - y| = 11

Case 1: 3-y = 11
-y = 8
y = -8.

Case 2: -3+y = 11
y = 14.

Since it's possible that y=-8 or y=14, INSUFFICIENT.

Statements combined:
Only y=14 satisfies both statements.
SUFFICIENT.

The correct answer is C.
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by CSASHISHPANDAY » Sun Jun 30, 2013 3:15 am
can u plz explain the concept in detail
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