#### Answer

$$-3,3$$

#### Work Step by Step

A quadratic equation of the form
$$x^{2}+bx+c$$
can be factored as
$$=(x+x_{1})(x+x_{2}),$$
where $x_{1}+x_{2}=b$ and $x_{1}\times x_{2}=c.$
To solve
$$(x^{2}-9)=0,$$
factor
$$(x^{2}-9)=(x+3)(x-3)=0.$$
Hence, the solutions are
$$x=-3, 3.$$