Answer
$x^2-0.01$
Work Step by Step
Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the given expression, $
(x-0.1)(x+0.1)
$, is equivalent to
\begin{array}{l}\require{cancel}
(x)^2-(0.1)^2
\\\\=
x^2-0.01
.\end{array}