Answer
$(m+8)^2$.
Work Step by Step
The given polynomial is
$=m^2+16m+64$
Write the the polynomial as $a^2+2ab+b^2$.
$=m^2+2(m)(8)+8^2$
Use perfect square trinomial pattern
$a^2+2ab+b^2=(a+b)^2$
We have $a=m$ and $b=8$.
$=(m+8)^2$
Hence, the factor of the given polynomial is $(m+8)^2$.
