(y-4)(y+4)

The expression \((y-4)(y+4)\) can be simplified using the difference of squares formula, which states that:

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

In this case, we can let \(a = y\) and \(b = 4\). Therefore, we have:

\[ (y-4)(y+4) = y^2 - 4^2 \]

Calculating \(4^2\):

\[ 4^2 = 16 \]

Putting it all together:

\[ (y-4)(y+4) = y^2 - 16 \]

So, the simplified form of the expression is:

\[ y^2 - 16 \]