For which of the following values of x is....

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For which of the following values of \(x\) is \(\sqrt{1-\sqrt{2-\sqrt{x}}}\) NOT defined as a real number?

A. 1
B. 2
C. 3
D. 4
E. 5

[spoiler]OA=E[/spoiler]

Source: GMAT Prep

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by Jay@ManhattanReview » Mon Apr 29, 2019 12:34 am
VJesus12 wrote:For which of the following values of \(x\) is \(\sqrt{1-\sqrt{2-\sqrt{x}}}\) NOT defined as a real number?

A. 1
B. 2
C. 3
D. 4
E. 5

[spoiler]OA=E[/spoiler]

Source: GMAT Prep
For \(\sqrt{1-\sqrt{2-\sqrt{x}}}\) to be a real number √(2 - √x) must be non-negative. Thus, 2 - √x ≥ 0 => 0 ≤ x ≤ 4.
Thus, the correct answer is E, x = 5.

The correct answer: E

Hope this helps!

-Jay
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by Scott@TargetTestPrep » Wed May 01, 2019 4:13 pm
VJesus12 wrote:For which of the following values of \(x\) is \(\sqrt{1-\sqrt{2-\sqrt{x}}}\) NOT defined as a real number?

A. 1
B. 2
C. 3
D. 4
E. 5

[spoiler]OA=E[/spoiler]

Source: GMAT Prep
Since √5 is about 2.2, we see that √(2 - 2.2) is negative, and taking the square root of a negative number would not give a real number as an answer..

Answer: E

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