Question: Factor completely. 81, minus, 16, x, squared
81−16x^2
1. **State the problem:** Factor the expression $$81 - 16x^2$$ completely.
2. **Recognize the formula:** This is a difference of squares, which follows the formula $$a^2 - b^2 = (a - b)(a + b)$$.
3. **Identify squares:** Here, $$81 = 9^2$$ and $$16x^2 = (4x)^2$$.
4. **Apply the difference of squares formula:**
$$81 - 16x^2 = 9^2 - (4x)^2 = (9 - 4x)(9 + 4x)$$.
5. **Final answer:** The completely factored form is $$\boxed{(9 - 4x)(9 + 4x)}$$.