Answer
$10(a+b)(a-b)$
Work Step by Step
Factoring the $GCF=
10
$, the given expression, $
10a^2-10b^2
,$ is equivalent to
\begin{array}{l}
10(a^2-b^2)
.\end{array}
Using $x^2-y^2=(x+y)(x-y)$ or the factoring of the difference of 2 squares, then the factored form of the expression, $
10(a^2-b^2)
,$ is
\begin{array}{l}
10(a+b)(a-b)
.\end{array}