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Taking Negative Sign in Modulus

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Taking Negative Sign in Modulus

by Uva@90 » Thu Nov 14, 2013 9:50 pm
Hi All,
I have a doubt while handling Negative Sign with Absolute Values

Example:

|5x-3| - |3-4x| >0

Here Can I replace it with this,

|5x-3|+ |4x-3| >0
Is this allowed ?

Thanks in advance.

Regards,
Uva.
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by theCodeToGMAT » Thu Nov 14, 2013 10:10 pm
I don't think you can do so..

|3-4x| is interchange with |4x - 3|

but, we cannot extract "-ve" sign from Modulus.

Was this observation in some question? if so, can you please share the question
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by [email protected] » Thu Nov 14, 2013 11:01 pm
Hi Uva@90,

It's important not to try to manipulate math concepts that you don't completely understand. It's far better to use the TESTing Values to define whatever patterns exist in the given information.

Here, we have:
|5X-3| - |3-4X| > 0

So let's just figure out whatever we can about permissible values that fit the given information:

Could X = 0? NO.
Could X = 1? YES.
Could X = -1? YES.

This means that "a shift" occurs somewhere around the value 0; this is the "hinge point" of the calculation and it's a piece of info that you can likely use to solve whatever question is attached to this info.

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by Uva@90 » Fri Nov 15, 2013 1:47 am
theCodeToGMAT wrote:I don't think you can do so..

|3-4x| is interchange with |4x - 3|

but, we cannot extract "-ve" sign from Modulus.

Was this observation in some question? if so, can you please share the question
Thanks Rahul,


Actually I trying to solve the problem in the below link,
https://www.beatthegmat.com/pls-explain- ... 71749.html

I thought of finding the range of X. It could be easy for calculation if that's is possible, that's why :P
(Unfortunate :( )

Regards,
Uva.
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by Uva@90 » Fri Nov 15, 2013 1:49 am
[email protected] wrote:Hi Uva@90,

It's important not to try to manipulate math concepts that you don't completely understand. It's far better to use the TESTing Values to define whatever patterns exist in the given information.

Here, we have:
|5X-3| - |3-4X| > 0

So let's just figure out whatever we can about permissible values that fit the given information:

Could X = 0? NO.
Could X = 1? YES.
Could X = -1? YES.

This means that "a shift" occurs somewhere around the value 0; this is the "hinge point" of the calculation and it's a piece of info that you can likely use to solve whatever question is attached to this info.

GMAT assassins aren't born, they're made,
Rich
Thanks Rich.
not to try to manipulate math concepts that you don't completely understand. It's far better to use the TESTing Values to define whatever patterns exist in the given information.
Ha ha.. Sure. I won't.

Regards,
Uva.
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by theCodeToGMAT » Fri Nov 15, 2013 1:51 am
Uva@90 wrote:
theCodeToGMAT wrote:I don't think you can do so..

|3-4x| is interchange with |4x - 3|

but, we cannot extract "-ve" sign from Modulus.

Was this observation in some question? if so, can you please share the question
Thanks Rahul,


Actually I trying to solve the problem in the below link,
https://www.beatthegmat.com/pls-explain- ... 71749.html

I thought of finding the range of X. It could be easy for calculation if that's is possible, that's why :P
(Unfortunate :( )

Regards,
Uva.
I could guess that ;) that's why I asked
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by Mathsbuddy » Sat Nov 16, 2013 11:01 am
Uva@90 wrote:Hi All,
I have a doubt while handling Negative Sign with Absolute Values

Example:

|5x-3| - |3-4x| >0

Here Can I replace it with this,

|5x-3|+ |4x-3| >0
Is this allowed ?

Thanks in advance.

Regards,
Uva.
As |3-4x|=|4x-3|, then the answer is no. Modulus is just the value without any sign, therefore changing a sign inside the modulus bars, does not change it.
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