SOLUTION: I am an online student for Algebra II and the program does not give explanations for problems entered in a specific way. I had a problem on a quiz today which I got wrong and have

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Question 605630: I am an online student for Algebra II and the program does not give explanations for problems entered in a specific way. I had a problem on a quiz today which I got wrong and have no idea why I got it wrong. Please explain how to simplify:
2/[3*cbrt(5)]
I tried to multiply both the numerator and denominator by 3*cbrt(5). The answer then would be 2*sqrt(5) over 15. But but this is wrong!
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I think your problem is the cube root.
Suppose you have +root%283%2Cx%29+
In order to get rid of the cube root sign,
you should do this: +root%283%2Cx%29%2Aroot%283%2Cx%5E2%29+
That equals +root%283%2Cx%5E3%29+=+x+
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So, for your problem,
+%28+2%2F%283%2Aroot%283%2C5%29%29+%29%2A%28+root%283%2C5%5E2%29%2Froot%283%2C5%5E2%29+%29+
+%28+2%2Aroot%283%2C5%5E2%29%29+%2F+%283%2Aroot%283%2C5%5E3%29%29+
+%28+2%2Aroot%283%2C25%29%29+%2F+15+
I checked this punching in numbers:
+root%283%2C5%29+=+1.71+
+root%283%2C25%29+=+2.924+
It checked out- try it