<span>-x^2 y^2 + x^4 + 4y^2 - 4x^2
= </span>x^4 -x^2 y^2 - 4x^2 + 4y^2<span>
= x^2 (x^2 - y^2) - 4 (x^2 - y^2)
= (x^2 - y^2)(x^2 - 4)
= (x + y)(x - y) (x + 2)(x - 2) (....using a^2 - b^2 = (a+b)(a-b) )
hope it helps</span>
The existence proof of the empty set is an absolute gem
Answer: Table C
Explanation: The X values match up with those on the graph!
