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It is a Yes/No question, asking if Y is an even integer.

Let's start with statement 2, it says X is an odd integer, no information is provided regarding Y. Hence Insufficient.
You can eliminate options B and D.

Statement 1: -
2y−x=x^2 - y^2
y^2 + 2y = x^2 + x
y(y+2) = x(x+1)

Now we have four possibilities,
x,y - Both Even
x - Even, y - Odd
x - Odd, Y - Even
x,y - Both Odd

The equation works only in the first and the third case, that is when either both x and y are even or when x is odd and y is even. We are only concerned about y being even. Hence, Sufficient - A
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If x and y are integers, is y an even integer?


(1) \(2y - x = x^2 - y^2\)

(2) x is an odd integer.

Statement 1: \(2y - x = x^2 - y^2\). \(2y\) will always be Even

\(=>y^2=x^2+x+Even\). Now irrespective of the value of \(x\), \(x^2+x\) will always be Even, because \(x\) is an integer.

Hence \(y^2=Even+Even=Even\). Sufficient

Statement 2: nothing mentioned about \(y\). Insufficient

Option A


Hello,

How come is it x^2 + x + EVEN?

Shouldn't it be - EVEN?

Also, even - even = even.
This means y^2 is even.
Which then should mean, y is even.

Please let me know if I have inferred this correctly.
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Statement 1 can be reduced to y(y+2) = x(x+1):
2y−x=x^2 - y^2
y^2 + 2y = x^2 + x
y(y+2) = x(x+1)

We can see x(x+1) will always be an even number, since one of the term here must be even. So y(y+2) must also be even. This allows us to confirm y is even since y and (y+2) will have the same even/odd properties.
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If x and y are integers, is y an even integer?

(1) \(2y - x = x^2 - y^2\)
Even - y = x + x^2

RHS will always be even thus, y is even.

SUFFICIENT.

(2) x is an odd integer.
Nothing about y or x's relation with y.

INSUFFICIENT.

Answer A.
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