a^2-16b^2

The expression \( a^2 - 16b^2 \) is a difference of squares. It can be factored using the identity \( x^2 - y^2 = (x - y)(x + y) \).

Here, we can rewrite the expression as:

\[ a^2 - (4b)^2 \]

Applying the difference of squares formula gives:

\[ (a - 4b)(a + 4b) \]

Therefore, the factored form of \( a^2 - 16b^2 \) is:

\[ (a - 4b)(a + 4b) \]