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Number Properties!

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Number Properties!

by Ahmed MS » Tue Oct 25, 2011 10:38 pm
Determine whether the following expression is POSITIVE, NEGATIVE or CANNOT BE DETERMINED with numerical examples!

Q: (-X) / (-Y)(-Z), given that xyz > 0


IS is NEGATIVE, but I have come up with CANNOT BE DETERMINED!



Please help me guys.
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by Ahmed MS » Tue Oct 25, 2011 10:41 pm
Ahmed MS wrote:Determine whether the following expression is POSITIVE, NEGATIVE or CANNOT BE DETERMINED with numerical examples!

Q: (-X) / (-Y)(-Z), given that xyz > 0


IS is NEGATIVE, but I have come up with CANNOT BE DETERMINED!



Please help me guys.

OA is Negative! Beg your pardon!
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by neelgandham » Wed Oct 26, 2011 2:19 am
Determine whether the following expression is POSITIVE, NEGATIVE or CANNOT BE DETERMINED

Exp: (-X) / (-Y)(-Z) = -(x/(yz)) (As -ve *-ve = +ve), given that xyz > 0

xyz >0 implies,
x = -ve, y = -ve and z = +ve or
x = -ve, y = +ve and z = -ve or
x = +ve, y = -ve and z = -ve or
x = +ve, y = +ve and z = +ve

Let us check the sign of the expression (-X) / (-Y)(-Z)= (-(x/(yz)) (As -ve *-ve = +ve)) in all the cases.

x = -ve, y = -ve and z = +ve, (-(x/(yz)) = - ((-ve)/(-ve * +ve)) = -ve
x = -ve, y = +ve and z = -ve, (-(x/(yz)) = - ((-ve)/(+ve * -ve)) = -ve
x = +ve, y = -ve and z = -ve, (-(x/(yz)) = - ((+ve)/(-ve * -ve)) = -ve
x = +ve, y = +ve and z = +ve, (-(x/(yz)) = - ((+ve)/(+ve * +ve)) = -ve

Hence Negative ![/b]
Anil Gandham
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by rooster » Wed Oct 26, 2011 2:25 am
One point to keep in mind as you approach this problem:

Even if n=negative, the negative sign in front still changes the status therefore even if n= -1

-n= 1 OR -(-1)

Just need to know the properties as neelgandham pointed out the options.

in order for xyz to be >0, all are negative or either 2 of the 3 need to be negative.
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