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ashikaverma13
GMAT 1: 640 Q47 V31
Posts: 128
11 May 2017, 11:56
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E
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89% (00:24) correct
11%
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What is the value of x?
(1) |x| = 4.
(2) x^2 = 16.
(1) |x| = 4.
(2) x^2 = 16.
I want to know how B is not sufficient here. Isn't it a general rule that square root of any number is always positive?
11 May 2017, 12:10
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ashikaverma13
What is the value of x?
(1) |x| = 4.
(2) x^2 = 16.
I want to know how B is not sufficient here. Isn't it a general rule that square root of any number is always positive?
(1) |x| = 4.
(2) x^2 = 16.
I want to know how B is not sufficient here. Isn't it a general rule that square root of any number is always positive?
What is the value of x?
(1) |x| = 4 --> x = 4 or x = -4. Not sufficient.
(2) x^2 = 16 --> the same here: x = 4 or x = -4. Not sufficient.
(1)+(2) Same two values from both: x = 4 or x = -4. Not sufficient.
Answer: E.
As for your question: when the GMAT provides the square root sign for an even root, such as \(\sqrt{x}\) or \(\sqrt[4]{x}\), then the only accepted answer is the positive root.
That is, \(\sqrt{16}=4\), NOT +4 or -4. Even roots have only a positive value on the GMAT.
In contrast, the equation \(x^2=16\) has TWO solutions, +4 and -4.
Hope it's clear.
General Discussion
ashikaverma13
11 May 2017, 14:12
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Bunuel
ashikaverma13
What is the value of x?
(1) |x| = 4.
(2) x^2 = 16.
I want to know how B is not sufficient here. Isn't it a general rule that square root of any number is always positive?
(1) |x| = 4.
(2) x^2 = 16.
I want to know how B is not sufficient here. Isn't it a general rule that square root of any number is always positive?
What is the value of x?
(1) |x| = 4 --> x = 4 or x = -4. Not sufficient.
(2) x^2 = 16 --> the same here: x = 4 or x = -4. Not sufficient.
(1)+(2) Same two values from both: x = 4 or x = -4. Not sufficient.
Answer: E.
As for your question: when the GMAT provides the square root sign for an even root, such as \(\sqrt{x}\) or \(\sqrt[4]{x}\), then the only accepted answer is the positive root.
That is, \(\sqrt{16}=4\), NOT +4 or -4. Even roots have only a positive value on the GMAT.
In contrast, the equation \(x^2=16\) has TWO solutions, +4 and -4.
Hope it's clear.
I think I understood but one more thing. So if, the statement B had said x = \(\sqrt{16}\) then it would have been sufficient?
but what is the difference if I, on my own am taking a square root of the statement B. That is my confusion. If I take square root of the entire statement B then won't it be:
\(\sqrt{x^2}\) = \(\sqrt{16}\) which, therefore, will lead to x =4?
unless I am doing something wrong by taking square root of the entire statement.
