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# absolute value problem

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Intern
Joined: 28 Jun 2008
Posts: 45

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13 Jun 2009, 15:07
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hey guys was wondering if anyone could explain how to solve this problem:

Is lxl = y-z?

(1) x+y=z

(2) x<0

Manager
Joined: 30 May 2009
Posts: 213

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14 Jun 2009, 09:45
1
KUDOS
Is lxl = y-z?

(1) x+y=z
Take x=3, y=1, then z=4
But |x|=3 <> y-z=-3

Take x=-3, y=1, then z=-2
In this case |x|=3 = y-z

So INSUFF

(2) x<0
Without knowing about y and z, this gets us no where. So clearly INSUFF.

Combining (1) and (2) though....
If x < 0
|x| = -X
|x| = - (z-y) {obtained from (1)}
|x| = y-z

Senior Manager
Joined: 07 Jan 2008
Posts: 384

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14 Jun 2009, 10:25
scorpio7 wrote:
hey guys was wondering if anyone could explain how to solve this problem:

Is lxl = y-z?

(1) x+y=z

(2) x<0

From 1: y-z=-x ==> cannot prove that |x| = y-z
from 2: x<0 ==> -x>0. cannot prove that |x| = y-z
But both ==> -x = |x|, while -x = y-z ==> |x| = y-z.

C is correct asnwer.
Re: absolute value problem   [#permalink] 14 Jun 2009, 10:25
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