2008 AMC 10B Problems/Problem 5

Problem

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

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

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2008 AMC 10B (Problems • Answer Key • Resources)
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