Answer
The statement given is TRUE
Work Step by Step
Recall that the definition $\sqrt{-a} = i\sqrt{a}$ must be applied BEFORE the other rules regarding radicals, therefore,
$\sqrt{-4}\cdot\sqrt{-9}$
$ i\sqrt{4} * i\sqrt{9}$
$ i^2 \sqrt{36}$
$(-1)(6)$
$$-6$$