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If x = 9a^2 and a < 0, then x^(1/2) =

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Carcass
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If x = 9a^2 and a < 0, then x^(1/2) = [#permalink] New post   09 Jun 2022, 03:00
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Question Stats:

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If x=9a2 and a<0, then √x=

(A) −3a
(B) 3a
(C) 9a
(D) 3a^2
(E) 81a

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A
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GreenlightTestPrep
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Re: If x = 9a^2 and a < 0, then x^(1/2) = [#permalink] New post   09 Jun 2022, 09:39
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Carcass wrote:
If x=9a2 and a<0, then √x=

(A) −3a
(B) 3a
(C) 9a
(D) 3a^2
(E) 81a


To avoid any silly mistakes, let's test a possible a-value.
For example, since we are told a is negative, it could be the case that a=−2, which means our equation becomes x=9(−2)2=36
If x=36, then √x=√36 =6

This means the correct answer will evaluate to 6 when a = -2
So, we'll plug a=−2 into the five answer choices to get:
(A) −3a = -3(-2) = 6. PERFECT!
(B) 3a = 3(-2) = -6. No good. Eliminate.
(C) 9a = 9(-2) = -18. No good. Eliminate.
(D) 3a^2 = 3(-2)^2 = 12. No good. Eliminate.
(E) 81a = 81(-2) = -162. No good. Eliminate.

Answer: A
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Ykayonu
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Re: If x = 9a^2 and a < 0, then x^(1/2) = [#permalink] New post   09 Feb 2024, 14:47
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From my POV, right out of the gate, since we know that a < 0, the answer must be -ve and only A) -3a fits. However, we can evaluate the equation by taking the square root of both sides to get √x = 3a but we know a < 0. Therefore, √x = -3a. Does this work Brent & Carcass?
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Re: If x = 9a^2 and a < 0, then x^(1/2) = [#permalink] New post   14 Feb 2024, 05:37
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It works like a charm sir :thumbsup:
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Re: If x = 9a^2 and a < 0, then x^(1/2) = [#permalink] New post   14 Feb 2024, 13:29
Haha thanks Carcass :please:
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Re: If x = 9a^2 and a < 0, then x^(1/2) = [#permalink]
14 Feb 2024, 13:29
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