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If (x - 1)^2 = 400 which of the following could be the value

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If (x - 1)^2 = 400 which of the following could be the value [#permalink] New post 20 Dec 2012, 08:07
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If (x - 1)^2 = 400, which of the following could be the value of x - 5?

(A) 15
(B) 14
(C) -24
(D) -25
(E) -26
[Reveal] Spoiler: OA
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Re: If (x - 1)^2 = 400 which of the following could be the value [#permalink] New post 20 Dec 2012, 08:09
Expert's post
Walkabout wrote:
If (x - 1)^2 = 400, which of the following could be the value of x - 5?

(A) 15
(B) 14
(C) -24
(D) -25
(E) -26


(x - 1)^2 = 400 --> x-1=20 or x-1=-20 --> x-5=20-4=16 or x-5=-20-4=-24.

Answer: C.
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Re: If (x - 1)^2 = 400 which of the following could be the value [#permalink] New post 13 May 2014, 09:36
Hi,

this is an interesting problem regarding the GMAT Club Math Book. I studied it and on page 15 it says:

When the GMAT provides the square root sign for an even root, the only accepted answer is the positive root. That is, NOT +5 or -5. In contrast, the equation x^2 has TWO solutions, +5 and -5. Even roots have only a positive value on the GMAT.

Due to this fact (which of course does not include this particular situation, because it's talking about the "sign"), I didn’t consider the negative root.
Maybe a phrase, which could be improved on the next issue :).
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If (x - 1)^2 = 400 which of the following could be the value [#permalink] New post 30 Jul 2014, 08:33
holdem wrote:
Hi,

this is an interesting problem regarding the GMAT Club Math Book. I studied it and on page 15 it says:

When the GMAT provides the square root sign for an even root, the only accepted answer is the positive root. That is, NOT +5 or -5. In contrast, the equation x^2 has TWO solutions, +5 and -5. Even roots have only a positive value on the GMAT.

Due to this fact (which of course does not include this particular situation, because it's talking about the "sign"), I didn’t consider the negative root.
Maybe a phrase, which could be improved on the next issue :).

That statement from the book still holds good, it says "when GMAT provides the square root sign" whereas in this problem you were explicitly calculating the square root of 400 rather than GMAT providing \sqrt{400}.
Hope that helps.
If (x - 1)^2 = 400 which of the following could be the value   [#permalink] 30 Jul 2014, 08:33
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