ANSWER
[tex]4,-4[/tex]
EXPLANATION
Given;
[tex]\frac{x^2+9x+18}{x^2-16}[/tex]
For the expression to be not defined, the denominator must be equal to zero.;
Hence,
[tex]\:x^2-16\:=0[/tex]
Add 16 to both sides;
[tex]\begin{gathered} x^2-16+16=0+16 \\ x^2=16 \\ \end{gathered}[/tex]
Find square root of both sides;
[tex]\begin{gathered} x=\sqrt{16} \\ x=\pm4 \end{gathered}[/tex]
