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If x is a positive integer greater than 1, is x! + x + 1 a prime number?

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If x is a positive integer greater than 1, is x! + x + 1 a prime number?

(1) x < 10
(2) x is odd

Official Answer

1 Best Answer

Answer: Can be solved using condition 2 Only. (B).
Since x is odd, then x+1 is even and x! is even . Hence x! + x + 1 is even . Hence it cannot be a prime number.
Using the Condition 1 : It cannot be concluded whether it is a prime no or not . eg :
If x = 4 then x! + x + 1 = 29 which is a prime no but if x = 3 then x! + x + 1 = 10 which is not a prime number .
 
Hence the questions can be answered using statement 2 alone .
answered Jun 22, 2014 by Associate (163 points)
selected Jun 22, 2014 by
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