Verified Answer :

exponental law

\(( \sqrt{x}) times ( \sqrt{n} )= \sqrt{xn}\) so
√(81y^5)=√81 times √(y^5)
√81=9 or -9
√(y^5)=y^2 times√y
answer is 9y^2 times √y or -9y^2 times √y