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15 Jul 2013, 23:41
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If x is an integer, what is the value of x?
(1) |23x| is a prime number.
(2) \(2x^{\frac{1}{2}}\) is a prime number.
GMAT Club test set the correct answer as (E), as they conclude x could be 1 or -1. But Is prime number can be negative? So my answer would be (D) as x=1
(1) |23x| is a prime number.
(2) \(2x^{\frac{1}{2}}\) is a prime number.
GMAT Club test set the correct answer as (E), as they conclude x could be 1 or -1. But Is prime number can be negative? So my answer would be (D) as x=1
16 Jul 2013, 21:33
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guhabiswasavijit
Prime numbers are always positive.
(1) |23x| is a prime number.
Here, x can be 1 or -1
x = 1: |23x| = 23 (a prime number)
x = -1: |23x| = |23(-1)| = |-23| = 23 (a prime number) (the mod converts the negative to positive)
(2) \(2x^{\frac{1}{2}}\) is a prime number.
Are you sure the actual question doesn't say \(2x^{2}\) is a prime number?
16 Jul 2013, 21:46
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guhabiswasavijit
Actually with the given options, answer must be B, as it would yield x=1.
However for the answer to be E, the statement 2 must have x^2 instead of x^1/2 as karishma pointed out.
