[tex]\bf 81h^8k^6\quad
\begin{cases}
81=9^{1\cdot 2}\\
h^8=h^{2\cdot 4}\\
k^6=k^{3\cdot 2}
\end{cases}\implies 9^{1\cdot \stackrel{\downarrow }{2}}h^{\stackrel{\downarrow }{2}\cdot 4}k^{3\cdot \stackrel{\downarrow }{2}}\implies (9^1h^4k^3)^{\stackrel{\downarrow }{2}}
\\\\\\
(9h^4k^3)^2[/tex]
