Answer
$49a^2-100$
Work Step by Step
Using the product of the sum and difference of like terms which is given by $(a+b)(a-b)=a^2-b^2,$ the given expression, $
(7a+10)(7a-10)
,$ is equivalent
\begin{align*}
&
(7a)^2-(10)^2
\\&=
49a^2-100
.\end{align*}
Hence, the product of the given expression is $
49a^2-100
$.
