Chapter R - Elementary Algebra Review - R.6 Rational Expressions and Equations - R.6 Exercise Set - Page 980: 4

The expression is undefined if $x=-1$ or $x=-8$.

A fraction is undefined, if the denominator equals to zero. Here: $x^2+9x+8=0$ $(x+1)(x+8)=0$ First solution if: $x+1=0$ $x=-1$ Second solution, if: $x+8=0$ $x=-8$ The expression is undefined if $x=-1$ or $x=-8$.