Answer
$(a-8b)(a-10b)$
Work Step by Step
The given expression, $
a^2-18ab+80b^2
,$ has $c=
80
$ and $b=
-18
.$
The possible factors of $c$ are $
\{ 1,80 \}
,\{ 2,40 \}
,\{ 4,20 \}
,\{ 5,16 \}
,\{ 8,10 \}
,\{ -1,-80 \}
,\{ -2,-40 \}
,\{ -4,-20 \}
,\{ -5,-16 \}
,\{ -8,-10 \}
$. Among these factors, the pair whose sum is equal to $b$ is $\{
-8,-10
\}.$ Hence, the factored form is
\begin{array}{l}\require{cancel}
(a-8b)(a-10b)
.\end{array}
