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poonam1279
- Master | Next Rank: 500 Posts
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To find if (x^2+1) * (x+5) is even
If either (x^2+1) or (x+5) is even or both are even then the product will be even. For this to happen x has to be odd
since odd*odd = odd
even*odd or odd*even = even
EVEN*EVEN = EVEN
Stmt I
x is odd
Exactly what we need
SUFF
Stmt II
each prime factor of x^2 greater than 7. This means each prime factor of x is greater than 7 since if x had a prime factor less than 7 then x^2 definitely has that prime factor. So x cannot be even as 2 is a prime factor of every even number.
This means x is odd
SUFF
Choose D)
