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Question

If x<0,then (-x|x|)^1/2
1. -x
2. -1
3. 1
4. x
5. x^1/2

lahoosaher · Answer

for (-x|x|)^1/2,

for x<0 , -x|x| = x^2
So , (-x|x|)^1/2= x

Answer : D

tharunv · Answer

Let's say x is -1
Then (-(-1)|-1|)^1/2 = (1)^1/2 = -1 or 1
Same is the case with 2, it would be -2 or 2

So what's the OA? Is it D?

tharunv · Answer

Ok got it now - (x ^ 2)^1/2 = x. It should be D.

nitindas · Answer

This is a question from GMATPrep.
And they say answer is -x.

I don't understand how could it be -x.

lahoosaher · Answer

MGMAT book says that for an even root , a non negative rooot of a number is valid .
so Answer must be D.

tharunv · Answer

Ok what we get as the final answer is x
But we started with x < 0
and what is the answer x - it is nothing other than -x. ie., - (-x) or -(-2)

So GMATPrep is correct - the answer is A
Funny how these questions can be the difference between above/below 700.

nitindas · Answer

Nice Explanation...!!

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