AMC 12 2008b Problem 7

For real numbers $a$ and $b$, define $a$$$b = (a - b)^2$. What is $(x - y)^2$$$(y - x)^2$?

(Solution)

\textbf{(A)}\ 0 \textbf{(B)}\ x^2 + y^2 \textbf{(C)}\ 2x^2 \textbf{(D)}\ 2y^2 \textbf{(E)}\ 4xy