\[\boxed{\mathbf{111}\mathbf{9}\mathbf{\text{.\ }}Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ a\sqrt{5} = \sqrt{5a^{2}}\]
\[2)\ b\sqrt{- b} = - \sqrt{- b^{3}}\]
\[3)\ x\sqrt{x^{7}} = \sqrt{x^{9}}\]
\[4)\ n\sqrt{m} = - \sqrt{mn^{2}};n \leq 0\]