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# Question on modulus?

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Director
Joined: 29 Nov 2012
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21 May 2013, 22:42
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For example the question is

x = I X I

then if x > 0 then X = X

and if X < 0 then X = - X

is this correct
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Current Student
Joined: 17 Apr 2011
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21 May 2013, 23:27
y = |x|
implies
y= x when x>=0
y= - x wen x<0

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VP
Joined: 02 Jul 2012
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Location: India
Concentration: Strategy
GMAT 1: 740 Q49 V42
GPA: 3.8
WE: Engineering (Energy and Utilities)

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22 May 2013, 00:08
I would add, if x = 0, x = |x|

A condition that is often overlooked and used especially in the DS section.
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Math Expert
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22 May 2013, 03:01
fozzzy wrote:
For example the question is

x = I X I

then if x > 0 then X = X

and if X < 0 then X = - X

is this correct

Absolute value properties:
When $$x\leq{0}$$ then $$|x|=-x$$, or more generally when $$some \ expression\leq{0}$$ then $$|some \ expression|\leq{-(some \ expression)}$$. For example: $$|-5|=5=-(-5)$$;

When $$x\geq{0}$$ then $$|x|=x$$, or more generally when $$some \ expression\geq{0}$$ then $$|some \ expression|\leq{some \ expression}$$. For example: $$|5|=5$$.

For more check Absolute Value chapter of Math Book: math-absolute-value-modulus-86462.html

DS questions on absolute value to practice: search.php?search_id=tag&tag_id=37
PS questions on absolute value to practice: search.php?search_id=tag&tag_id=58

Tough absolute value and inequity questions with detailed solutions: inequality-and-absolute-value-questions-from-my-collection-86939.html

Hope it helps.
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Re: Question on modulus?   [#permalink] 22 May 2013, 03:01
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