Solve for: sqrt(216k^4)

Expression: $\sqrt{216k^{4}}$

Apply radical rule: $\sqrt{ab}=\sqrt{a}\sqrt{b},\quad$ assuming $a\ge0, b\ge0$

$=\sqrt{216}\sqrt{k^{4}}$

Simplify $\sqrt{k^{4}}:{\quad}k^{2}$

$=\sqrt{216}k^{2}$

$\sqrt{216}=6\sqrt{6}$

$=6\sqrt{6}k^{2}$