Answer
$(a+7)(a+9)$
Work Step by Step
$a^2+16a+63$ has no common monomial factors.
=$(\ \ \ \ \ \ \ \ \ )(\ \ \ \ \ \ \ \ \ )$
=$(a\ \ \ \ \ \ \ )(a\ \ \ \ \ \ \ )$
=$(a+\ \ )(a+\ \ )$ All terms in the trinomial are positive.
=$(a+7)(a+9)$ 7 and 9 have a sum of 16 and a product of 63.
