Chapter 6 - Section 6.2 - Factoring Trinomials Whose Leading Coefficient is 1 - Exercise Set - Page 436: 78

$(a+b)(x-9)(x-4)$

First, there is a GCF (of all terms), GCF=$(a+b)$ $...=(a+b)(x^{2}-13x+36)$ Searching for two integer factors of $36$ such that their sum is $-13...$ we find $-9$ and $-4.$ = $(a+b)(x-9)(x-4)$ All are prime, factorization is complete