Answer
$\color{blue}{\left\{-7, 0, 9\right\}}$
Work Step by Step
RECALL:
Zero-Factor Property:
If $ab = 0$, then either $a=0$ or $b=0$ or both are $0$.
Use the property above to obtain:
\begin{array}{ccccc}
&4x=0 &\text{or} &x-9=0 &\text{or} &x+7=0
\end{array}
Solve each equation to obtain:
$4x=0
\\\frac{4x}{4}=\frac{0}{4}
\\x=0$
or
$x-9=0
\\x=0+9
\\x=9$
or
$x+7=0
\\x=0-7
\\x=-7$
Thus, the solution set is $\color{blue}{\left\{-7, 0, 9\right\}}$.
