Chapter 3 - Polynomial and Rational Functions - 3.5 Rational Functions: Graphs, Applications, and Models - 3.5 Exercises - Page 380: 120

$(x+4)(x+1)(x-3)(x-5)$

Step 1. Use the known zeros $-4,-1$ with synthetic division as shown in the figure. Step 2. Use the quotient to find the rest zeros: $x^2-8x+15=0$ or $(x-3)(x-5)=0$ which gives $x=3,5$ Step 3. Thus the numerator can be factored as $(x+4)(x+1)(x-3)(x-5)$