Simplify square root of 9i^4

$\sqrt{9 i^{4}}$

Rewrite $i^{4}$ as $1$ .

Rewrite $i^{4}$ as ${(i^{2})}^{2}$ .

$\sqrt{9 {(i^{2})}^{2}}$

Rewrite $i^{2}$ as $- 1$ .

$\sqrt{9 {(- 1)}^{2}}$

Raise $- 1$ to the power of $2$ .

$\sqrt{9 \cdot 1}$

Multiply $9$ by $1$ .

$\sqrt{9}$

Rewrite $9$ as $3^{2}$ .

$\sqrt{3^{2}}$

Pull terms out from under the radical, assuming positive real numbers.

$3$