The expression $4x^2 - 1$ can be factored using the difference of squares formula, which states that:

$a^2 - b^2 = (a - b)(a + b)$

Here, we can identify $a^2 = (2x)^2$ and $b^2 = 1^2$. Applying the difference of squares formula:

$4x^2 - 1 = (2x - 1)(2x + 1)$

So, the factored form of $4x^2 - 1$ is $(2x - 1)(2x + 1)$.

Would you like further details or have any other questions?

Here are five related questions:

1. How do you factor a quadratic expression like $ax^2 + bx + c$?
2. Can you factor $9x^2 - 16$ using the same method?
3. What is the difference of squares formula and when is it applicable?
4. How can the difference of squares be applied to solve quadratic equations?
5. How do you factor a polynomial with more than two terms?

Tip: When factoring expressions, always check if the difference of squares formula can be applied, especially if you see two perfect squares separated by a subtraction sign.