For x and y integers, is xy even?
(1) x2 + y2 is odd.
(2) x + y is even.
Answer should be A
ODD + EVEN = ODD, otherwise EVEN
ODD * ODD = ODD, otherwise EVEN
So, xy to be even atleast one of them should be EVEN.
(A) X^2 + y^2 = ODD then one of them must be ODD and the other should be EVEN (as you know square of even is even and square of odd is odd)
clearly says, xy must be EVEN
(B) says X + Y = EVEN, so either both X and Y are ODD or both X and Y are EVEN.
If both are ODD - then XY = ODD and
if both are EVEN then XY = EVEN so, B can not answer the Question.
Please post OA
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