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AkhilAggarwal
Given ‘a’ and ‘b’ are positive integers, is the number b^2+7b+ab even?

(1) (a+ b)(a - b) is a multiple of 2
(2) (a+2)(a-2) is a multiple of 4


a and b are integers.

\( b^2+7b+ab=b(b+7+a)\) will be even when
(i) b is even.
OR
\( b^2+7b+ab=b(b+7)+ab\)
Now b(b+7) will be even in every case as b and b+7 will give one as odd and other as even.
Thus, if a is even, the expression will be even
(ii) a is even.

Thus, if we can show that any of a or b is even, the answer is yes. If both are odd, then answer is no.

Let us see the statements.
(1) (a+ b)(a - b) is a multiple of 2
It just tells us that both are of same property, that is either both are even or both are odd.
Insufficient

(2) (a+2)(a-2) is a multiple of 4
If a is odd, then (a+2) and (a-2) will be odd and not even.
Thus, a is even.
Sufficient

B
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