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Gmat prep- Absolute Value

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Gmat prep- Absolute Value

by khurram » Tue May 27, 2008 6:57 am
Why is the answer not 1. X/X=1

The square root sign cancels the square sign, so we have x/x ?or because it is x^2 we have to account for x being neg or pos.

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Khurram
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by AleksandrM » Tue May 27, 2008 9:18 am
Yes, because X could be negative or positive, you want to take its absolute value over x.
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by khurram » Tue May 27, 2008 11:36 am
thanks
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by khurram » Tue May 27, 2008 11:43 am
do we not take if square root of x^2, as positive unless stated otherwise.

can you please give an example. I am not totally clear how this works.

eg x=2 so 2/2=1??

but ans is absolute x/x

so 2/2/ =1 or -2/2=-1.

or ans is e to show that we can have two answers, -1 or 1. that would make sense.

so ans stops one step before the last step ???

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by AleksandrM » Tue May 27, 2008 5:10 pm
-1 is not the answer because when you plug -1 into the equation you will end up with an imaginary number. Remember:

-1^2 = - (1 * 1) = -1 and the sqroot of a negative number gives you an imaginary number. Some might be mislead by thinking that x^2 is (x)^2, which it is not.

The answer cannot be zero because you are told that x is not zero. If x is zero, that gives you a zero in the numerator and denominator. Anything divided by a zero is undefined.

It will not be x, because xs will cancel out.

Let me make it easier for you. Stop thinking about plugging in numbers on this one.

When you simplify sqroot x^2 you end up with + or - x. You need to get rid of the or.

Therefore, to get the answer, you take the absolute value of x over x. That is as far as you simplify the expression.
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