Let $(a, b)$ be any point in the domain of $f$. Then, we have:
$$\lim_{(x, y) \to (a, b)} (xy, x^2 - y^2) = (ab, a^2 - b^2) = f(a, b)$$
Since the limit exists and is equal to the function value at $(a, b)$, the function is continuous at every point in its
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