Answer
$(5n+2)^2$.
Work Step by Step
The given polynomial is
$\Rightarrow 25n^2+20n+4$
Write the the polynomial as $a^2+2ab+b^2$.
$\Rightarrow (5n)^2+2(5n)(2)+2^2$.
Use perfect square trinomial pattern $a^2+2ab+b^2=(a+b)^2$.
We have $a=5n$ and $b=2$.
$\Rightarrow (5n+2)^2$.
Hence, the factor of the polynomial is $(5n+2)^2$.
