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vinayreguri
- Junior | Next Rank: 30 Posts
- Posts: 29
- Joined: Sat May 07, 2011 6:16 am
Hi,
(x^2-y^2) = (x+y)(x-y)
From(1): x-y is even.
So, x and y are both odd or both even.
In both cases x+y is even as well. So, (x+y).(x-y) is even*even = multiple of 4
Sufficient
From(2): x+y is even.
So, x and y are both odd or both even.
In both cases x-y is even as well. So, (x+y).(x-y) is even*even = multiple of 4
Sufficient
Hence, D
