(a-b)(a+b)

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

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

In this case, we can identify \(x = a\) and \(y = b\). Therefore, we have:

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

So, the simplified form of \((a - b)(a + b)\) is:

\[ a^2 - b^2 \]