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.

⇒ ax² + 4a²x – 3bx – 12ab = 0

⇒ ax(x + 4a) -3b(x + 4a) = 0

⇒ (ax – 3b)(x + 4a) = 0

⇒ x = 3b/a, -4a