(X-y)(x+y)

The expression \((x - y)(x + y)\) can be simplified using the difference of squares formula. This formula states that:

\[ (a - b)(a + b) = a^2 - b^2 \]

In your case, let \(a = x\) and \(b = y\). Applying the formula, we get:

\[ (x - y)(x + y) = x^2 - y^2 \]

So, the simplified form of the expression \((x - y)(x + y)\) is:

\[ x^2 - y^2 \]