#### Answer

$(x+10)(x-10)$

#### Work Step by Step

The expressions $
x^2
$ and $
100
$ are both perfect squares (the square root is exact) and are separated by a minus sign. Hence, $
x^2-100
,$ is a difference of $2$ squares. Using the factoring of the difference of $2$ squares which is given by $a^2-b^2=(a+b)(a-b),$ the expression above is equivalent to
\begin{array}{l}\require{cancel}
(x)^2-(10)^2
\\\\=
(x+10)(x-10)
.\end{array}