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If x = 9a^2 and a < 0, then x^(1/2) =
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09 Jun 2022, 03:00
09 Jun 2022, 03:00
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Question Stats:
42% (00:43) correct
57% (00:56) wrong based on 21 sessions
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If \(x = 9a^2\) and \(a < 0\), then \(\sqrt{x} =\)
(A) −3a
(B) 3a
(C) 9a
(D) 3a^2
(E) 81a
(A) −3a
(B) 3a
(C) 9a
(D) 3a^2
(E) 81a
Part of the project: GRE QCQ & PS 3 Questions Every One DAILY Challenge - (2022)
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GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
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Posts: 6218
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Re: If x = 9a^2 and a < 0, then x^(1/2) =
[#permalink]
09 Jun 2022, 09:39
09 Jun 2022, 09:39
3
Carcass wrote:
If \(x = 9a^2\) and \(a < 0\), then \(\sqrt{x} =\)
(A) −3a
(B) 3a
(C) 9a
(D) 3a^2
(E) 81a
(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 \(\sqrt{x} =\sqrt{36}\) \(= 6\)
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
Re: If x = 9a^2 and a < 0, then x^(1/2) =
[#permalink]
09 Feb 2024, 14:47
09 Feb 2024, 14:47
1
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?
