Answer
$(x-10)^2$.
Work Step by Step
The given polynomial is
$=x^2-20x+100$
Write the the polynomial as $a^2-2ab+b^2$.
$=x^2-2(x)(10)+10^2$
Use perfect square trinomial pattern
$a^2-2ab+b^2=(a-b)^2$
We have $a=x$ and $b=10$.
$=(x-10)^2$
Hence, the factor of the given polynomial is $(x-10)^2$.
