\[*\ \ :a^{6} \cdot a^{5} = a^{9}\]
\[*\ \ :a^{6} = a^{9}\ :a^{5}\]
\[*\ \ :a^{6} = a^{4}\]
\[*\ = a^{4} \cdot a^{6}\]
\[*\ = a^{10}.\]