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