SOLUTION: I must have left out some information I am looking to rationalize the following denominator {{{18/root(3,81)}}} I get as far as 6 over 3rd root 3 , but can I reduce furthe

Break up 81 this way

81 = 9‧9 = 3‧3‧3‧3 = 3⁴



To get rid of the 3rd root in the denominator we need 
an exponent of 3 which is a multiple of 3.
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To get that we multiply top and bottom by  ∛3²
 



We multiply tops and bottoms, we multiply under the
radicals on the bottom so we'll have 3⁶ under the radical
which has an exponent of 6 which is a multiple of 3



Now we get rid of the radical on the bottom by
dividing the power of 3 which is 6 by the index of
the root which is 3 and get 3² 




Then we make both 3²'s into 9



Then the 9 cancels into the 18 and gives 2 on the top


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So that's the answer 2∛9

Edwin