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mathtard
\[\sqrt[3]{-729x^3}\] simplify
http://www.wolframalpha.com/input/?i=%28-729%29%5E%281%2F3%29%3D-27 i for square not for cube http://www.mathway.com/answer.aspx?p=calg?p=SMB203:(-729)?p=22?p=?p=?p=?p=?p=0?p=?p=0?p=?p=
=-9x 27i is positvie wrong