Appendix A - Review - A.4 Factoring Polynomials - A.4 Assess Your Understanding - Page A40: 80

$(x+1)(x+4)$

To factor the second-degree polynomial $x^2 + 5x + 4$, we have to find integers whose product is $4$ and whose sum is $5$. That is, we have $1$ and $4$, where $1+4=5$ and $1\times (4)=4$. Thus $$ x^2 + 5x + 4=(x+1)(x+4) .$$