Answer
$(3x+2)(x+2)$
Work Step by Step
The two numbers whose product is $ac=
3(4)=12
$ and whose sum is $b=
8
$ are $\{
2,6
\}$. Using these two numbers to decompose the middle term, then the factored form of the given expression, $
3x^2+8x+4
$,is
\begin{array}{l}\require{cancel}
3x^2+2x+6x+4
\\\\=
(3x^2+2x)+(6x+4)
\\\\=
x(3x+2)+2(3x+2)
\\\\=
(3x+2)(x+2)
.\end{array}
