GMAT Prep Math Problem

[nnshyam]

GMAT Prep Math Problem Solving Question:

If x<0, then (-x|x|)^0.5 is ?

1) -x
2)-1
3)1
4)x
5)x^0.5

Can anyone explain me this?

[jrankoth]

GMAT Prep Math Problem Solving Question:

If x<0, then (-x|x|)^0.5 is ?

1) -x
2)-1
3)1
4)x
5)x^0.5

Can anyone explain me this?

I'm getting D, x.

(-x|x|)^.5 is the same as (-x|x|)^1/2, which is the same as sqrt (-x|x|)
Since x<0, -x = -(-x) = x, and |x| = x.
Therefore, we need to find the value of sqrt (x*x) = x.

Whats the answer?

[nnshyam]

Official Answer is A

But i believe there is some flaw in the question.

If x<0 then |x| = -x and so sqrt(-x.|x|)==>sqrt(-x.(-x))==>sqrt(x^2)

sqrt(x^2) can be +/- x i am not sure how to narrow it down to -x.

[Guest83]

nnshyam,

Using a number may help you understand the problem better. For example, let x = -9.

Therefore, -x|x|^.5 = (-(-9)|-9|)^.5 = (9*9)^.5 = 9

Therefore the answer is -x (A)

Hope this helps.