The factor of a² - 2a + 1 - b² is _____?

(a−1−b)(a−1+b)

(a+1−b)(a−1+b)

(a−1−b)(a+1+b)

None of these

Given the expression a² - 2a + 1 - b²:

Step 1: Factor the perfect square trinomial

a² - 2a + 1 = (a - 1)²

So, the expression becomes (a - 1)² - b²

Step 2: Apply the difference of squares formula

(a - 1)² - b² = (a - 1 - b)(a - 1 + b)