It's impossible. y² is ≥ 0 , so -y² ≤ 0 . Clearly 2 > 0 .
I don't know what Ackbeet was thinking.
Yeah, all I wanted to do was point out that the product of two numbers can be positive if both of the multiplicands are negative. I hadn't gotten so far as to determine if there actually were any numbers in the set or not. So the answer is, I wasn't thinking as deeply as was necessary!