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.

⇒ 7(x + 5 – x + 1) = 6(x – 1)(x + 5)

⇒ 42 = 6x² + 24x – 30

⇒ x² + 4x – 12 = 0

⇒ x² + 6x – 2x – 12 = 0

⇒ x(x + 6) – 2(x + 6) = 0

⇒ (x – 2)(x + 6) = 0

⇒ x = 2, -6