When x and y are integers, is x+y an even?

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When x and y are integers, is x+y an even?
1) x^2+y^2 is an even
2) (x+1)^2+(y+1)^2 is an even

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by Max@Math Revolution » Wed May 25, 2016 2:42 am
X and y in the conditions 1) and 2) can end up being both odd or both even.
The answer to both conditions are 'yes', which make the conditions sufficient.
The correct answer, hence, is D.
- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.