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is (x^2 + 1) (x + 5) an even number?

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is (x^2 + 1) (x + 5) an even number?

by sanju09 » Wed Apr 08, 2009 5:58 am
If x is an integer, is (x^2 + 1) (x + 5) an even number?

(1) x is an odd number.

(2) Each prime factor of x^2 is greater than 7.



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by scoobydooby » Wed Apr 08, 2009 6:07 am
1) x is odd
=>(x^2 + 1) (x + 5)= (odd+odd)*(odd+odd) =even
sufficient

2) Each prime factor of x^2 is greater than 7
=>each prime factor of x is greater than 7. 2 is the only even prime, so all these prime factors are odd=> x is odd
sufficient

hence, D
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