#### Answer

$(\sqrt H+3)^2$

#### Work Step by Step

The first term is $\sqrt H$ squared, the last term is $3$ squared, and the middle term is twice the product of these two terms. Now we can factor the trinomial into a binomial squared.
$H+6\sqrt H+9$
$=(\sqrt H+3)(\sqrt H+3)$
$=(\sqrt H+3)^2$