Answer
$(x+9)^2$
Work Step by Step
The given polynomial is
$=x^2+18x+81$
Write the the polynomial as $a^2+2ab+b^2$.
$=x^2+2(x)(9)+9^2$
Use perfect square trinomial pattern
$a^2+2ab+b^2=(a+b)^2$
We have $a=x$ and $b=9$.
$=(x+9)^2$
Hence, the factor of the given polynomial is $(x+9)^2$.
