In factorization, we write the middle term of the quadratic equation either as a sum of two numbers or difference of two numbers such that the equation can be factorized.

⇒ 4x² + 2(a + b)x – 2(a – b)x – (a – b)(a + b) = 0

⇒ 2x(2x + a + b) – (a – b)(2x – (a + b)) = 0

⇒ (2x – (a – b))(2x + a + b) = 0