Algebra Help Radical notation
posted by Tim .
My problem is:
4 sqrt 81
I know the answer is 3, but I do not know how they got it.

write that as 81^(.25) which is (81^.5)^.5
that is
sqrt ( sqrt 81 )
81 is nine times nine
so
sqrt ( sqrt 81 ) = sqrt (9)
but 9=3*3 so
sqrt (9) = 3 
Thankyou, I don't know why I did not think of that. I came up with every other number imaginable but that. I think I was trying toooooooooooooo hard!

5^1/7 in radical notation

(64)^2/3