Answer
$(x-4)(x+7)$
Work Step by Step
The given expression, $
x^2+3x-28
,$ has $c=
-28
$ and $b=
3
.$
The possible factors of $c$ are $
\{ 1,-28 \}
,\{ 2,-14 \}
,\{ 4,-7 \}
,\{ -1,28 \}
,\{ -2,14 \}
,\{ -4,7 \}
$. Among these factors, the pair whose sum is equal to $b$ is $\{
-4,7
\}.$ Hence, the factored form is
\begin{array}{l}\require{cancel}
(x-4)(x+7)
.\end{array}