Answer
$x=\{-1,8\}$
Work Step by Step
Equating each factor to zero (Zero Product Principle), then the solutions to the given equation, $
(x+1)(x-8)=0
,$ is
\begin{array}{l}
x+1=0
\\\\
x=-1
,\\\\\text{OR}\\\\
x-8=0
\\\\
x=8
.\end{array}
Hence, $
x=\{-1,8\}
.$