Appendix A - Review - A.4 Factoring Polynomials - A.4 Assess Your Understanding - Page A40: 42

$(x+1)(x+8)$

To factor a second-degree polynomial $x^2 + 9x + 8$, we have to find integers whose product is $8$ and whose sum is $9$. That is, we have $1$ and $8$ where $1+8=9$ and $1\times 8=8$. Thus: $$ x^2 + 9x + 8=(x+1)(x+8) .$$