Bunuel wrote:
If x and y are positive integers, is x^2 – y^2 an even integer?
(1) 3 is a factor of x + y.
(2) x – y is an odd integer.
In what case can x^2 – y^2 be even?
Both x and y are even. then E^2-E^2= Even
or Both x and y are odd. Then O^2 - O^2= Even.
(1) 3 is a factor of x + y.
Let's say x+y = 3, where x= 2 and y = 1
In this case x^2 – y^2 is not even
If x+y= 6, where x=4 and y=2
In this case x^2 – y^2 is even
Not sufficient.
(2) x – y is an odd integer.
For x-y to be odd. either x or y is even and the other integer is odd.
In both the cases, square of one integer will be odd and the other integer will be even. And O-E or E-O will be odd.
Sufficient.
B is the answer
_________________
I welcome critical analysis of my post!! That will help me reach 700+