Answer
$x^2-49$
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+7)(x-7)
,$ is equivalent to
\begin{array}{l}\require{cancel}
(x)^2-(7)^2
\\\\=
x^2-49
.\end{array}